Last I checked, giving a LEO crap isn't against the law. As long as everything Grisham did was legal (and as far as we can tell, it WAS), the LEO's acted inappropriately and illegally.
If what you're saying is correct, then I guess the police have the right to infringe on the 1st Amendment also. As an example, calling a cop a "pig" might not be the smartest thing to do, but if they arrested/detained you as a result, that would be illegal. That's the point. Capitulating to Police simply because they're police might save you some immediate problems (going to jail, etc) but you might be giving up your rights just to make your life easier right now. That's why Grisham talked about the "hard right" over the "easy wrong."