He says that - 'language changes all the time' - in his defense of NOT changing the definition or at least having a definition that matches the old meaning.
I've watched this three or four times now and TBH it's not all that clear what his point is beyond "we should be able to use the words men and women" and, like, ok? That's it? Also, who are the Taliban-defending leftists or the people who think they shouldn't put boy or girl on birth certificates or are destroying people's lives for using the term "woman?"
I don't think this is a great clip, but it's pretty funny how much stronger a communicator he is than Peterson.