If this movie was released by Miramax, then how come it made fun of them? Does Kevin Smith hate them for the whole Dogma crisis or something? What's the point?
Biting-the-Hand Humor — kind of like how The Simpsons is always making fun of Fox despite it being the channel that produces and broadcasts the show. Smith's a humorist and the people he works for can be a valid source of humour as well.
It helped that the Weinstein brothers, who were running Miramax at the time, were huge fans of Kevin Smith's movies, and loved the film's story.
The jokes about Miramax are mostly good-natured ribbing, not truly caustic attacks.