I've just banned the user @Hypnotoad for some repeated bad-faith behavior. Some of this is still visible in their history if you want to look, but some has also been edited or deleted which will make it less obvious (this post explains some of it, not all). I also know their reddit account (but hadn't looked through it previously) and there's a bit of bigotry and general poor behavior there as well.
No, I did not send them a warning, and no, I don't intend this ban to be temporary. I know that some of you will think this is too harsh, but to be honest, some of you are way too forgiving. It will be completely impossible to maintain any semblance of a high-quality community if we have to constantly give low-quality, trollish users the benefit of the doubt. Good users don't want to (and shouldn't have to) spend most of their time on a site trying to educate other people how to behave. That gets tiresome extremely quickly, and results in the good users just finding somewhere else to spend their time instead.
So... in terms of discussion topics, feel free to give opinions on this specific ban, as well as thoughts about how this type of decision should be made in general. Having some standards is absolutely necessary though, Tildes can't possibly serve as both a high-quality discussion site as well as a "troll education space".