Well you're right about how people should be treated fairly and if somebody's trolling you, they should get at least a warning for it if not a ban or something.
But you have a very very bad history here on the boards, including posting a thread about committing a possible felony.
So when a moderator responds to a situation, they have that note staring them in the face.
When another user posts something borderline, and they have no bad history, it's possible a moderator could let them off with a PM warning or something of that nature. Or even a short temp ban that you don't even know the person was given. Or even a permaban. Who knows.
But - the point is, if you are seen as threatening someone on the boards, with your posting history, it carries a different context. And speaking personally, while I sympathize with what you're saying about being frustrated by the situation, if I were to read a post of yours even remotely threatening another user, I would ban you instantly and permanently.
Because of your posting history.
I'm not saying you actually threatened somebody, I'm just trying to give you some perspective on why mods do what they do.
If you think you're not being treated fairly though, you should bring it up. And again, if you would simply state the actual details - including the screen name you're talking about, maybe in a little calmer and more easily understandable way, you might get somewhere.
No guarantees, but you never know.