Personally, calling the cops should only be a response when you're okay with bringing a potentially deadly wildcard into the situation. If it's already a potentially deadly situation, or you're okay with making it potentially deadly, then sure go ahead and tell the cops to come out there and do something. If there's a way to de-escalate the situation or remove the deadly situation without the cops, then that's great and definitely don't involve them, but when it's a violent enemy who has obviously committed crimes, I don't see why you'd endanger yourself trying to deal with them when there's a violent gang that you can just tell to go fight them. Like, if you can trick a cop into doing something anti-fascist why the hell not?