Well, if all was as you put across, then they were definitely wrong for how they acted towards you and them reporting your signature seems utterly rediculous (it's a good quote whether you're religious or not), however, it's understandable why they did harass you. I'm sure it was a case of them feeling harassed in the first place and simply doing the same in return.

As for the admin, well, the idea that he wanted it removed seems preposterous, but I'm sure being banned was down more to the argument (in which we don't know what was said) than the signature, as he could have simply disabled it.