Ok Bee, I see what you're saying. It can be alarming to see people running round doing stuff you don't understand the motivation for or have the same feelings about. What you described isn't exactly my cup of tea, either. But having said that, I think it's a bit restrictive to assume that because you don't see or believe in anything you can't see or experience in some physical way that such things don't exist, or that others might not be able to percieve them. While it seems on the balance of probabilities unlikely they do, it's still possible and so we must make room in our big world for those people too. And it is a big world.
The only problem would be if they were physically harming someone - I won't go as far as saying psychologically harming, as this is much more difficult to quantify. Trying to judge what's psychologically normal often seems more like simply comparing it to what happens to be the majority conformity of the time. For example people who don't aspire to a career and aren't ambitious about money and social kudos are often thought of as a bit odd or eccentric, thanks to the majority preoccupations of this sad world. But it may be that THEY are the sane ones, not the mad ones who are running round chasing their tail trying to make a few dollars more than last year.