He seems to be answering criticism from Clymer.

Edit: in terms of the election (which he has still not officially declared for) fighting with Clymer makes him look good. Clymer is a psycho and has gotten into public battles with religious figures and conservative commenters on Twitter multiple times. He's known to the base already as a villain.

Grenell is showing off for Republican voters by being dignified and reasonable against a crazy leftist transwoman.

The GOP seems sincerely concerned (to me) that Republicans in California are too homophobic to be relied on to turn out for Grenell. They're engaging in an entirely separate pre-campaign to sell him to his own voters. That's what Caitlyn is about, in my opinion.