Have them arrested for what? Being a wanker on public transport?

While it could be seen as harassment, it could also take time away from police who might otherwise be dealing with actual violence, rather than the fear/implication of it.

I've been googling for possible existing pressure groups or campaigns about this, and so far drawn a blank, other than reclaim the night, which is a bit more specific, although relevant, as the sort of casual arrogance/aggression i've described happens all the time, and not just at night. It's just at night, the risk of actual attack is far higher.