I am not a lawyer but I don't think a fair use defense is the way to go in this case. The "free promotional value to the plaintiffs" angle is a serious stretch too. The lawsuit between Paramount Pictures and the crowdfunded Star Trek spin-off "Prelude to Axanar" is heating up again. With a trial scheduled for early next year, both parties have submitted motions for summary judgment. The defendants argue, among other things, that their fan-film clearly falls under fair use.