I've also seen instances of individuals defending free speech because they hold unpopular (or sometimes even hurtful) opinions and want to be taken seriously, or want a megaphone – both of which they are free to demand but which no one is obligated to give them.
I signed the MIT Free Speech Alliance's petition and signed up for its newsletter because I agree with the aims of the movement, but I had the impression that some of the alumni leading the alliance have political motives, or are less angry about the loss of freedom at universities [1] than they are about the social opinions of the rising generation, which worries me somewhat.
[1] which IMO ought to be the paragons of free speech.