Among strangers, I think most people would head for the group they think they’d have the most in common with. A lone woman would probably head for a group of women, a lone man to other men. A pensioner would most likely join other pensioners rather than the group of teenagers, and vice-versa. That doesn’t make a person racist, sexist, ageist or anything else-‘ist’ – people just seek what’s most familiar in an unfamiliar situation.
The Royal Family thing is a bit different to racism, I suspect. I reckon it’s more a case of natural curiosity combined with a blundering lack of tact.