Mostly agree with OP.
Baalrunners don't only Baalrun to provide service to others. They also do it to speed up their own leveling. So they are dependent on other people joining. This involves them acting a little classy towards others.
OP did nothing wrong, he only asked WHY he shouldn't help kill Baal. The answer is probably that the runner has very high MF%, and maybe wanted the drops for himself, which is fair to me.
But it does not justify suddenly going all out, flaming, harassing, hostiling and continuously shutting him out of the runs.
That kind of behaviour, along with every single person here show absolutely no sign of understanding, intelligence or empathy, inclines me to think that there are a looot of psychopaths around this forum. Nobody gives the guy the benefit of the doubt, or even logically analyzes the situation properly. Most people just takes the hard law for what it is: If someone makes a game, it is that person's rules, and nothing else matters.
OP is correct: Even though you make the game, ethics still play a part. It doesn't give you the right to act like a fucking shitbag to others. He could have just not answered, as long as OP didn't attack Baal, it would have been alright.