Cops like that give law enforcement a bad name. 99.9% of cops do a great and very difficult job. It is that small percentage of thugs that get into law enforcement and get of on the power and getting to hide behind badge while being a thug to the general public. You want to reform the police then get rid of those type of "cops."The bikers are as$holes, cops or not.
Either lose the drummer for that gig, you know the same scum will float in with him again... Or if drummer has sufficient standing in the band, ask him what he’d do, making clear what the problem is, and that future gigs there requure another drummer.
cannot really answer without knowing specific personalities and musical abilities etc beyond that.... it’s a tough business.