I can’t speak for others, but I don’t make fun of people for having different beliefs than I do. I sometimes argue when I think someone is doing something wrong (not just a chumrah, actually doing something wrong, such as people davening way after the zman on a regular basis).
What bothers me is when people try to say they’re better because they do things differently – and this thread is a good example! The OP said “someone frummer than you”. Just because you may keep a chumrah that I don’t doesn’t make you more frum than me. You may be more machmir, but that doesn’t mean more frum. We’re different, that’s all. Only Hashem knows who is doing things “better”, because only Hashem knows what’s going on in everyone’s heart.
When my kids see things which are different than the way we do things, we explain to them, “Different people do things differently, and that’s ok. We do things this way, and they do it hat way. They’re both right!”