I think it's an overstatement to suggest that he's "ridiculing safe spaces". He's making the point that, a lot of what now passes for the left (not really left at all, in my opinion, but liberal identity politics freaks) seems to have given up on anything other than talking to itself. Whether that's through trying to silence those with whom they disagree e.g. no platforming, shouting then down, or trying to get them to shut up by smearing them.
And, whilst I don't agree with everything he says, there's some truth in that point. It's not an effective tactic for any meaningful change.