You can also try - I don't know how hard this is since I'm a big, scary looking guy myself - to simply let go of your emotions and don't worry about what happens. Do it a few times and see how they react at least. I.e. never mind the outcome, think that it's okay even if you die in horrible pain or anything like that, just let go. You do this simply by becoming apathetic for a while, just relaxing until you almost become a zombie. I find that you can get people relaxed if you do that. People who are bullies are insecure with themselves and have to prove something, like rearden says, so acting as if he's a criminal might lead him to think that he looks like a criminal and it might piss him off. Where people like that went wrong is most assuredly when it comes to social skills and getting friends without almost having to bash their skulls in and force them, so they feel hated by everyone and put up a tough front, and they don't like to admit it of course, so acting sympathetic won't help either - that'd probably be worse.
Then you can always, which is probably a better tip, act like you're already his friend in how you approach him, but not in what you say. In that case he might get suspicious and get angry too. I hope some of this works for you.