Because the definition of a troll has somehow got twisted, a poster that comes to have fun, ok, take the piss out of a few idiots along the way and possibly know or at least think they know a thing or 2 about the site is automatically a target and banned very easily and once banned are called a troll..
Yes there are plenty of actual trolls on this forum but not every poster that is banned is a troll, a lot just rub the mods up the wrong way, that's all it takes really, it is their sand pit and they can throw whomever they wish out and we all just have to either help them build their sand castle or bugger off...