I'm going to interrupt a bookstore manager who ended up being very rude
Do you know why they were rude?
I've heard the reason many times.
Interrupting is rude behavior. You should wait for an appropriate time to speak.
You can't prevent free speech. They are acting like they own the store just because I plan to hand out pamphlets.
I agree, but you are not handling the situation well. It is better to let the manager know how you feel and get your way than to just do the same thing they are doing.