Okay, lets assume that Guardia kept the sword, which has no proof (I believe he returned it to Denadaro). Porre was still the one that attacked Guardia.
I'll anylize your inital arguement here, so we can have some points to debate here... Firstly know that I'm dismissing your Dalton ideas as crap. Dalton theorys crack me up. Anyway.
Now while the Masamune was in the Frog's possession, Crono's (as the Red knife) and Melechior's, it is regarded as holy and good. Something to stand against evil. Yet it went with Frog back to 600 where he lived to a ripe old age (purely speculation of course Razz ) and the Sword went on. It no doubt was in Guardia's possession.
Why is it no doubt in Guardia's possession? Its a powerful, holy sword, and I think frog would be responisble enough to return it to where it came from; Denadaro. Further support comes from the fact that Radius probably killed Garai at Denadaro (see another topic for this), in 1005. However, he did kill him after the massacre, so it remains to be said. But regardless, its pure speculation its Guardia one way or another.
Now we have four hundred years. Four hundred years of both good and bad men having access to it. Each successive person imbuing it with their own emotions. But there was regularity. But obviously it would have been exposed to negativity. Masa and Mune would be sleeping, believing Lavos done with and their purpose finished. So they wouldn't regulate the power. All it would have taken was the right evil man to come by (hell maybe Yakra masquerading as the Chancellor) to have his feelings transferred over. Hate, malice, cruelty and greed. Now the Sword has had affect on people using it (as apparent with Karsh/Dario scenario). Could the evil feelings led to some political unrest. So the peaceful kingdom of Guardia wasn't so peaceful?
Okay, for this, lets just assume your right, Guardia has the Masamune. And lets also assume that for some reason, Masa and Mune aren't doing their job. People continue getting exposed to it, good and bad. Now, this brings me to my first point, a few posts back. The point of the Masamune's corruption. It was after/maybe during the Fall. The Masamune was not corrupted prior to the fall. Its clearly seen in its "Holy" sword form in that scene. There was no clearly evil man that transfered its feelings and evil emotions to the sword, not until Guardia falls at least. Therefore, the sword is not evil, and therefore could not make Guardia unnaturally corrupt.
[Paraphrasing the Dalton crap out, Porre invades because they see Guardia as evil and corrupt, and therefore must be overthrown.]
I've already established that the Masamune could not have corrupted Guardia any more than otherwise. Also, remmber, Porre is not the good guys. Guardia castle was burned. Villages in Guardia were burned, and people slaughtered. And remmber, at the time of Guardia's fall, Crono and Marle were still around. Crono, married into the Royal family, and hailed as a hero (see Moonlight Parade). King Guardia was a noble leader, for the most part. We do not see any corruption in the Guardian government, even after the game has been one, and we are in Keystone 1 timeline, which the fall still took place in.
A lot of this ties Dalton in. But Dalton isn't needed. Motive for a Dalton-less Porre nation? Well like I said, continued influence of a steadily more and more evil Masamune on Guardia and its higher ups (as it would no doubt be kept in the Castle) would cause political unrest leaving things open for a revolt. Who else but disgruntled Guardia Knights joining the first rebellious leader synthesized with Porre's military (though once again that might not have existed.) As The Guardia military always considered itself honorable and just (more emphasized in 600 AD but no doubt carried on) it is plenty of motive to leave a politically unrest and injust Guardia in favor of Porre, who comes out looking golden.
This goes back to assuming Guardia was corrupted, and Porre came to save the day...
Other factors in the political unrest? Well the King being put on trial and the subsequent battle in the courthouse (which will have been spread like fire with rumors abound.) The subsequent unrest of whether the King was guilty or not. Things like Crono's scheduled execution (which anybody knowing Crono would know is sham and would mistrust Guardia, and on the inverse, anybody believing Crono evil questioning Crono's pardon.) And the young Fritz, caught with a band of thieves (Radical Dreamers?).
The King was falsely put on trial, and the charges were dismissed. And it was a public trial. Plenty of people in the courtroom. Also, it would have been well known that an Evil Monster who wanted to take over the kingdom was falsly putting King Guardia on trial. Crono was pardoned, and people held him as a hero. See Moonlight parade.
What proof do you have that Frog returned the Masamune first off? The similarity between the scene in which Garai was killed and Denodoro? Well you realize the exact same scene is also the Divine Dragon Falls? Even the inside of the cave?
Sure there is a similarity in appearence to Denodoro. But like you said, Garai's death happened after the Fall.
Now Frog. He was fiercely loyal to the Kingdom of Guardia and Queen Leene in particular. Also, such a symbol as the Masamune which defeated Magus would no doubt be greatly desired. The King and Queen would keep it (with good intention in mind).
What exactly do you have against Dalton theories? They are a bit of an out there thing. A random element, but with Fate (computer and otherwise ) there are very little random things. I guess it was Random that Kid's pendant resembled Schala's and subsequently, Marle's.
I'm not saying the King was corrupt. And who said the government needs to be corrupt. Bill Clinton was said to be corrupt simply because of his sexual escapades when he helped the economy. George Bush is supposedly corrupt cause of his extreme religious ideas and his personalized war, but some people hail him as one of the best presidents.
The point? A government can appear corrupt without being so.
Masa and Mune weren't doing their job. Or else there wouldn't have been a demonic Masamune, a cursed sword of evil. I guess you forgot how they suddenly woke up after Dario was defeated. I guess you forget how they go "I think we've done something bad."
How do you know? Somethign contributed to Porre's rise to power. An either continually corrupt or seemingly corrupt Guardia. Where exactly are you getting your information of Guardia's government from 1000 to 1005?
Once again, was there a Massacre? I'm under the impression that the Massacre was what warped it into the red looking blade. The sword was seen as it WAS, but that doesn't mean it hadn't had something less then good imbued into it which would translate into the rest of the people in the castle. I mean the power of the Masamune managed to make an entire island demon infested. Could a Masamune that is only slightly corrupted (not enough to change shape yet) not cause some influence? Greed isn't neccessarily evil, but it is still negative.
Porre wasn't the good guys, true. But that doesn't matter. I'm talking about perceptions. They SEE themselves as the good guys. They seem the castle being destroyed as a good thing. And after some of the Massacre someone encounters the Masamune. Someone who so enjoys killing and destruction that they take the Sword and burn the villages and slaughter people.
The official consensus was that Crono was a hero. But are the guards that get the crap kicked out of them by Crono in his jailbreak going to believe that?
People evacuated the court room after Crono broke in and the battle began. Charges were dismissed, but people talk. People losing faith in a government, corrupt or not, can lead to rebellion.
Tell me. Was it public knowledge that Crono defeated Lavos? Did the King go and say "Hey everybody, This kid traveled through time, beat Magus personally, and then joined forces with him to defeat Lavos."
Anybody can join a celebration. But all it takes is a single suggestion for someone to question and that gets the ball rolling.