No, its not that. The Sounders came to RFK Stadium and won the 2009 U.S. Open Cup fair and square. Can't hate them just for being a good team.
Instead, we hated them because of the extremely presumptuous nature of their fans. Because they thought they deserved to host the Open Cup Final due only to their high attendance, rather than due to all the actual factors that go into that decision. Because they claim past trophies from their minor league days when trying to measure up to our trophy case, but conveniently ignore the past only when it suits them. Because their stadium is always effing full.
Let me be clear though - it wasn't jealousy. Never. If you're a Sounder fan and want to call us jealous, I'm liable to start hating you again.
So why don't I hate them anymore? Well the idea of a presumptuous fanbase has now been expanded throughout the entire Pacific Northwest. I don't see Portland Timbers fans being any less insufferable than Sounders fans. But mainly, I don't hate the Sounders anymore because they play entertaining attractive soccer. And they do things the right way. Their team is built how good MLS teams are supposed to be built - with plenty of American role players, supplemented with talent from the lesser nations of South and Central America. That's how the United teams of the 1990s were built. It sucks, but there's a vague air of familiarity to the Sounders.
I don't hate the Sounders anymore because there's a growing list of teams that I hate more. The Best Team Ever Assembled On Paper tops that list. Even Real Salt Lake's failed pursuit of #TheQuad seemed more annoying than Seattle's pursuit of a third consecutive Open Cup.
And finally, I also don't hate the Sounders anymore because I kind of love playing them. United is still undefeated at Qwest Field / CenturyLink. Bring it on.