It's always been the case in protest movements that you need to be a little careful who you let into your planning circle, especially if they suggest you commit crimes. This goes double if it's someone you only know over the Internet.
I heard that saying too, “if a stranger tries to make you do something illegal, it's a cop” or something close to that. Isn't it the principle of a sting operation?
That's a myth purposely spread by cops in order to fool people. Even if it was true, unscrupulous cops looking for promotions would be breaking it like all the other rules they routinely ignore.