Everything you said in your post, if Billi is truly a troll, is very spot-on. Except maybe this:
Reacting to an obvious troll with blatant hostility is not uncalled-for.
Actual trolls thrive on negative attention. So reacting with hostility and a stream of invective may help you vent, but it's not going to discourage them. Since getting our proverbial goats is what they want, we are actually giving them what they want by doing that. Also, reacting with a hostile stream of invective against any registered poster is still against the FAQs, and thus may incite a mod to intercede.
There is also another consideration that applies to you as an individual, my friend. You're a nice guy and a good-hearted person, so reacting like that to anyone is just totally not you.