I can’t count how many times, in yeshiva, I was mocked and imitated for my pronunciation of the cholam as “oh.”
David, I’m sorry you went through that. Please understand though that in essence it had nothing to do with the pronounciation. It was more likely kids who wanted to lord something over someone else. I’m not excusing them AT ALL. But you could easily pick anything (kippa type, suit color, tie choices…) and those kids (and even adults) will decide its a “religious” thing and mock others.