This is an interesting topic that seems to have gotten bent around. This is an absolutely shitty experience. The only thing I would suggest is to make sure you're not hanging out with the type of people who would pull this shit. For this very reason, I only roll with small groups and rarely out and about in clubs or whatever. The last thing I want is for some shit to go down when I'm all fucked up.
I agree with the whole lameness of the PLUR thing. To me, PLUR is only a mantra for little raver kids to justify their stoney existence. Look, drugs are bad. I use them, most people reading this will and have used them, but at the end of the day I will teach my kids to stay away from them.
Finally as it relates to coke and aggressive behavior: There is no question people become more aggressive after a few lines. However, a vast majority of people can use and not get involved with this kind of violent, irrational behavior. My bet is this incident had more to do with your attacker's frame of mind, peer pressure, and bad decision making than it did with any drug.