I commented on this before so will give my view again.
The term is offensive and (I think...) that's a pretty well known fact. I *suspect* Gilman knew that as he was a history major, and reportedly interested in the Korean War (link below). It's not a crazy reach to assume he at the very least took a class on WWII at some point for his degree in UI. Therefor you can make a good guess that he knew it was offensive. With that said, he apologized, and I don't think has said it again, so that can be that.
Edit to add: Whether he (or you) care about not offending people...well that is irrelevant. Once you put on that Team USA singlet you represent your country and you better do it well and be a good ambassador.
I do find a lot of his stuff cringey, but each to his own. I suspect he puts a ton of pressure on himself to be like T&T, probably not healthy.