Who gives a fuck about his height. Ezra Levant is a Jew from Canada grifting civic nationalism who does not give two fucks about Ireland. Justin Barrett is an Irishman who wants to end mass immigration into Ireland and to deport immigrants. You don't have to like Barrett but don't shit on him when he is trying to achieve what we all want.
I actually missed that bit, I must have tuned out at the end when he started with those cringe nicknames for Barrett. I don't think Barrett did particularly well in this exchange, being caught off-guard, but Levant was seemingly caught off-guard too and could offer nothing in response but the obvious height jokes and fed accusations, then later making a video inviting his subscribers to join in the name-calling, and then a lame domain registration trick.
My first impression was that he was genuinely surprised and amused by Barrett, but I think you might be right, he's probably seething about it. I'm also now wondering whether he did actually know about Barrett beforehand.