People who used to do drugs, but then switch and get all preachy to you!
Yes! I HATE this.
I'm perfectly cool accepting the sobriety of someone in my company. In fact, I don't even consider it polite to ask about or point out the fact that someone isn't drinking or just passed on that blunt -- that's their business, and none of mine. Plus, if I'm using drugs or alcohol socially, it's the socializing, not the drugs, that's important.
But please, don't rub it in my face repeatedly that you don't drink / use, whether your sobriety is newfound or longstanding. (Good for you. Want a fucking gold foil star??) Well, I DO drink / use, and I'm perfectly fine with that, so you best be fine with me enjoying this too, if you want to hang out with me and my friends when we're enjoying chemical forms of fun. I don't bend my brain when I'm hanging with a crowd that isn't doing the same. Nor do I talk about getting fucked up in that sort of company. I wish people who prefer to remain sober, if they're perfectly aware that they're going to be hanging with a crowd that doesn't wish to remain sober, would extend the same courtesy.
If you come to a social gathering unawares, and realize too late that people there are putting something in their brains that you're not comfortable with, you do no one any favors by leaving in a loud huff of righteous indignation or scorn. Just thank the host politely and leave unobtrusively.
The above is definitely a group-wide buzzkill I've experienced before. Its risk of occurring is, sadly, a large part of why friend groups often unintentionally draw their borders based on drug use or lack thereof, including tobacco.