I'm sorry to hear you had this experience. I think you did the right thing though. I personally am probably like Boar-Ral in that I can't do anything if someone confronts me. My adrenaline skyrockets and I usually have to sit down for about 20-30 minutes if it's something bad (like what you experienced). It kinda sucks.
At least I have a g/f now who would stand up for me if she was there. My ex just thought I was being irrational every time someone seriously stepped on my toes.
Anyway, the only advice I can offer, since I think I'm in a similar situation being at college (I don't have classes every day though):
1. Never park anywhere predictable. Park in different areas, at different times so that someone has a harder time of knowing that you'll be at Point A at Time X. Luckily I don't have to drive to campus most of the time (I live about 1 mile away) so I walk. But when I have to go, I try to vary the time and day. If you're driving to classes, just try to move around in the lot I suppose. I used to hide my H2 in the back corner of the lot where hardly anyone went when I used to commute. I figured it either would be very safe as no one saw it, or it would be a major target. After two years, I had no incidents so I guess it worked out ok.
2. If you're going to do work after dark, park under the lights. Even better if you can park in front of a video camera. I also try not to drive to campus mid-day because there are WAY too many people walking around.
3. Obviously, lock your doors. I sometimes fold in my mirrors too, hoping they will be less easy targets.
4. When you return to your truck, do a walk around. Make sure no one slashed your tires, clogged the exhaust, or vandalized the vehicle in any way. Just in case someone did something, at least you can call the cops before you get home and find out.
5. Hope for the best! I usually find trash on the hood or shoved in the door handles when I come back to the truck if it's been over an hour. People just can't seem to resist bothering it.
I f'cking hate Massachusetts and don't really know why I went back to the school I did. Almost everyone hates the Hummer up there, and I'm one of only 3 that drives around town. I try not to look anymore, but I can safely say I get the middle finger at least once a day. I'm trying to transfer into a good school nearby here in South-Central PA for the fall so I can get away from all the damn greenies.
I feel for you. Best of luck!
Oh, and finally:
I learned this from former Marine who told me try not to carry anything to attack someone that would show intent to harm. Carry something that you could use as a weapon that serves another daily purpose, i.e. Pocket Knife. Helps your defense in court if you have to defend yourself in a situation like this. He carried a sharpened camp shovel that was re-painted and bear mace.