Anecdotally, FWIW. I've been a vegetarian for about ten years. I'm not religious, but came to this decision after a lot of thought and reflection about my own ethics. I have no illusions that my behavior will help animals, meat packers, etc.; I just wasn't comfortable being a party to that system any longer.
I've been surprised, at times, that others can interpret this personal decision about my own behavior and beliefs as some "social cudgel" that I am wielding against them. I guess it doesn't take much to leap from "oh, are you a vegetarian?" to "you must think eating meat is unethical," to "you must think I'm evil for eating this burger," to "annoying snobby vegetarians, always acting superior and rubbing it in your nose."
Anyway. That hipster buying his fair-trade coffee might not be doing it to insult you. It might be something he's read about, thought about, and decided he cares about. He might figure that mostly it's an empty gesture, but maybe it'll do some good. If you want to buy some other coffee, he might be totally OK with that. Of course, YMMV.