Because he is The Little Guy, and there is a massive and highly publicized campaign by the US government against him. This is him doing what he can to fight back.

I think it says something that he never did anything with the patent until now, I believe that he has good intentions and no desire to be a patent troll. Given his unique situation, and his flair for drama and unorthodoxy, I think it makes perfect sense.

Maybe for the same reason the masses rally around companies and gov'ts that do it.