Unfortunately I'm not really sure where that thread could reasonably be split. Historically we've only split threads to preserve continuity when they veer way off topic. Someone spitting in the face of a newcomer on her welcome thread is obviously obnoxious and rude, but it's not really technically off-topic. I don't know how we could start splitting threads to remedy assholery without taking a big slide down the slippery slope toward behavioral moderation here.
As I said on that thread I think the on-topic and off-topic comments are unfortunately pretty thoroughly entangled there, so I'm not even sure which posts it would make sense to split. But hopefully the derailment is largely over now.