It's possible that the BLM either had a run in with another person from the server, and decided to stereotype all from it when he took your joke personally.
From the sounds of it, the fact that he had better gear than you, and didn't know how to do the second boss of WP... sounds like he's been carried by someone and is sore about that already. So your joke hit home a bit more than it should have.
Other thought is that he's just a pr**k and wanted something to blame your attitude on instead of you, yourself, to avoid a verbal fight. XD