It's not a slippery slope if YouTube's existing policies are already abused in such a manner. Hell, I would go so far as to conjecture that they're actually doing this to enable the trolls. Just think about how much easier this makes their job.
"My video was flagged & deleted, but it didn't violate any policies."
"Okay, what was it about?"
"Well, I was arguing that Christianity has historically enabled widespread persecution, while suppressing science."
"Ah. That sounds offensive. Good day to you, sir."
And those 2 guys in the video are fucking scumbags.