Well, the thing about that is, it's the comics. They can come along at any point and say "oh wait, that never happened, they were doombots, or skrulls or whatever", whereas this movie has the potential to take out any future sequels to Iron man, Captain America, the hulk and Thor with their respective casts. Which would be bad, because the Iron man movie made people love tony stark even after the idiocy that was civil war. And Whedon usually just does the same thing over and over again. Quippy dialogue, ridiculously overpowered waif-ish girls, reusing the same actors over and over again for said waifs, the list goes on...
And why are they giving this gimp control of what'll probably end up being the biggest film of the decade? What has he done recently, as a director, that succeeded? Firefly? no. Dollhouse? fuck no, even after fox canceled a superior show to give it a second season. Serenity, his big debut film as a director? no and that was essentially just a longer episode of firefly.
And it's never his fault when something goes wrong with one of his things, whether he's a writer or a director, is it? Oh no. Alien: resurrection was the cast's fault! Ron Perlman must of fucked it up. Or Sigourney Weaver! Dollhouse got screwed by fox, nevermind the second season that the ratings sure as hell didn't justify. Bugger. Whedon inspires furious nerd rage.
When in deadly danger, when beset by doubt, run in little circles, wave your arms and shout.