It's a business. Nothing wrong with the actors trying to promote a movie, helping people who pay their checks.
Sometimes they come out after a few years and bash the movies they were in and usually it's in bad taste. Kinda like what Hugo Weaving did with the first Cap. That was just a low blow. If you don't like the movie you're in - save it for the dinner table. Just comes off as being ungrateful to people who picked you for a part.
Critics and the GA don't owe anything to film studios so basically they can go to town

Which reminds me... Going back to my original review from last week...