Next time, hold the protest in your parents’ basement and don’t allow anyone else in. If anyone does “monitor” it without a court order you almost certainly have a case.
If you want attention and do it in public, you are probably going to be seen and if you allow anyone to join you may get people you don’t expect.
I go to lefty protests and photograph them. I’ve found them to be far more suspicious than right wing or Tea party protests.
Tea partiers will happily pose with their signs.