I don't think that people have a problem with Budsquad being in open. They understand that it's the way ESEA rules work and that unless those rules change, there's nothing to be done about it.
The reason people are upset is that all preseason and even for most of the regular season the offclass teams put forth this 'lol we're just playing for fun' message, but as we all saw, that changed as soon as their elimination became possible. The same thing happened with r5. As soon as there was the chance they wouldn't make playoffs, they went to mainclasses and took that playoff spot from some other team who had been working all season for it. Budsquad did the same thing. When they realized that they would not win on the roster that they'd picked from the start, they just switched a LAN capable scout onto his main class and he carried (as expected).
That's why I frankly have a lot of respect for Quantum Flux, because at least they made it clear from the very start that they wanted to win and that they were going to play on their main classes rather than give everyone this song and dance about how they're just loveable bros who just wanna play TF2 together (by the way, I'm sure that's true for Budsquad, and it's clear that they enjoy playing games together, which is cool and I don't fault them for that). It's just frustrating to see the switch back to main classes as soon as the going gets tough.
Big shoutout to Meat Market though, almost managing to pull out a victory despite the mainclassing and despite the client issues.
Good luck in the grand finals guys, and go Quantum Flux! (I never thought I'd be saying that, but here we are)