If you have a glass of water in your hand, you are drinking. Maybe you're not drinking alcohol, but calling it "pretending to drink" is just silly.
We're talking about parts of human psycology like not having the same posture as the rest of the group. Of course it's prejudice, but it's also real and difficult to be aware of when it's happening to you.
Also, nobody is showering their drink on you if you don't participate, so blowing your blunt smoke in their face is a much bigger asshole move for me.
No, PCP is known to make users violent beyond what alcohol would do. And increased alcohol consumption correlates with less ability to act violently, because at some point the drinker is going to be unable to move, while PCP does not degrade one's motor skills.
I'm approaching my mid-30s and never had anyone "encourage" me to put the water down and suck on a beer. Nor do I think wheeling a keg into the office is the same as a manager encouraging you to drink.
You definitely stand out when you're in a drinking context and your hands are in your pockets. There's something that can feel distrustful about that in some scenarios. I'd encourage non-drinkers to at least learn to play along and have some beverage in their hand.
A lot of our creep-detector software seems to kick in when someone isn't playing along with social ritual, and complaining that you have to play along doesn't really serve you. They're just basic social skills.