They rose from nothing and didn't owe anyone blind allegiance. No legendary or historic roots like some other great houses in Westeros. But they should be proud that a commoner was able to rise to royalty and the the rest of the royalty class didn't accept them and continue to spit on them!!! Sure there are some bad apples but when you are sh_tted on for your entire existence what else would you expect?
Here's to House Frey!!!
Robb broke his oaths to Walder. Robb owed Walder for the previous service that the Freys have given for Robb's war campaign. The wedding of Edmure and Roslyn should be considered payment for that. The new deal has not been paid for by either side. Robb broke his oath to Walder so Walder felt like he doesn't have to honor any promises he makes to the Starks.
Question. Assuming the Wot5ks was concluded and peace was reached on both sides with no punitive penalties. Unrealistic, I know,