With all due respect I don't think that this is what happened here. That's fine if he felt no need to help, to problem is when you go out of your way to let someone, someone who is trying to learn, that you think they aren't worth your time due to the tone of their post. I understand where the OP is coming from, the frustration at trying to learn something and constantly hitting roadblocks. Was he a little sarcastic? Yes, however I would be too if I couldn't find any help. This situation was escalated by the fact that his cry for help was met with a core contributor taking the time to tell him he wasn't going to help. I would compare that to going up to a homeless man and telling him you weren't going to give him any money. There just wasn't a good reason to post something like that.
However, to your last point, I can see how it'd be challenging to convey your stance that you won't allow uncivil discourse other than how he did so. If you go ahead and respond normally, you're just reinforcing the bad behavior, ergo it makes the "discourse must be civil" an empty promise/threat. Perhaps he could have replied, with a caveat that further uncivil posts would be ignored, but I can also see getting tired of that sort of behavior (and as a former forum mod, continually having to 'remind' people of the rules that they've already agreed to wears out really quickly).
