1st i'm not trying to argue, really just trying to flesh out this mental process.
2nd your example doesn't really help your argument.
A cop might respond to a call to "check it out". Not all calls like this would result in an arrest, ergo it's not illegal.
Again, If you follow someone home and they call the cops and say, "he's following me" and you say, "SO, i'm just walking".
They might tell you to stop or else, but at THAT POINT, chances are they aren't gonna do shyt but take your name in case the person you were following shows up dead.
It's fuked but it is what it is.
Also, if someone calls the police saying "there's a suspicious so and so" those don't always end up in arrests either. Sometimes people are just walking and if it's on a PUBLIC STREET then they can do that. If they happen to be walking the same way you are is that "stalking" all of a sudden?
Cops try to be "pro-active" where they can, but in most cases they really respond to CRIMES ALREADY COMMITTED or in progress. They respond to suspicious calls in an attempt to thwart some things, but ultimate in a lot of those instances there really are no crimes broken.
Im not sure what you're position is here. Just because a certain set of behaviors or activity doesnt result in an immediate arrest every time, does not make it lawful activity. Yes, there is a legal gray area when it comes to stalking or harassment, but again, my initial point (and one you keep trying to dance around for some reason) is that GZ was not within his legal rights to follow TM. Here is stalking as defined:
"STALKING.—The term ‘stalking’ means engaging in a course of conduct directed at a specific person that would cause a reasonable person to—(A) fear for his or her safety or the safety of others; or (B) suffer substantial emotional distress."
People are trying to make GZ's activity as legal as a casual stroll in the park. This is not true.