I think it's fair enough to call him a hero by standing up for the natural law even at the risk of his life, but he is absolutely not a martyr.
And by the word "hero" I mean a hero on a natural level, similar to a solider who gave his life fighting for his country. But this is no way establishes any sort of probability about his eternal salvation. We are told by God that in order to be saved we must belong to His Church and live a life free from mortal sin.