Sure, parody is allowed under US law. But is it allowed under Twitter's terms of service? And to what extent? Because when you play in their sandbox, you play by their rules.
{FU isn't really a logo, though. It's not even in the same font.
Also brubaker you're hellbanned and I can't figure out why.
He didn't use their logo, he made a satire on the logo to comment on the situation. You can't be passing off if you are doing commentary.
He specifically said he did it in order to gain twitter followers from those confused by the relationship between him and the conference.