He didn't even let them play 10 seconds into the round. He pulled the plug out of the console and did nothing but rage the rest of the stream, not even commentating on the matches going on, which is more disrespectful to the lesser known players.
He could have handled it professionally - which he by no means did. He unplugged the console, got up, and screamed at them to "Get the fuck out." Arturo later goes to say "The better players are at fighting games the stupider they are in real life." But then says the players are what are going to kill the FGC and keep them from going MLG.
It doesn't take more than 10 seconds to know when players are colluding, and its not just him but a lot of people who noted what was going on. Spooky is the only one who acted on it though.
Sanford doesn't play Balrog, I don't think he ever has. This isn't a "oh heres some secret tech" type business, this is a top player picking a character he knows nothing about in the grand finals where he should be using his main or a strong secondary. Chris G didn't use Yang at any point until then, why would him using it in the Grand Finals be seen as an average and normal thing when his Sakura would be the best choice?
And the fact that no officals stepped in to stop him tells a lot as well.
Spooky unplugged them, got them off the stream, and they probably went somewhere else to play. Simple as that.
If KDZ picked Lobo and DJT picked Joker in the Grand Finals at EVO, you can be promised someone would've pulled the plug really quickly. You don't disrespect people like that, it doesn't matter who you are. If you made it to the finals as Sakura, play Sakura. Don't play a character you have no actual experience with while giggling with your buddy on someone elses time and payroll.