"they didn't like us or the party much at all"
Wow, you're not joking, that police operation must have cost a fortune. When they do that stuff with flanking and teargas you have to organize into a single group upwind of them, preferably with the rig in the middle. c.f. UKTek 2015. With the crowd spread thin you're vulnerable to getting picked off individually by snatch squads and pulled behind the line when some dick inevitably throws a bottle from the back. Exciting stuff.
Seriously the Czech police look paramilitary and are likely to break your bones with a baton and stand on your throat in the van. I'd think twice about partying loudly in public and wouldn't even consider acquiring unless I had first hand knowledge and good local connections.
Prague is beautiful though and whilst I've only been as a tourist I'm told there are some very cool cats living there. Expect a good time but take care and learn from locals.
We're only truly alive when we're dancing.