I don't have a preference between the XSX and the PS5 except I probably will favor the PS5's controller, and I definitely like the look of the XSX more. I also understand that the XSX will have at least some backwards compatibility (what the Xbox One currently has...initially anyway) all the way back to the original Xbox, so I definitely prefer that to only one system's worth of BC. I don't even really have an opinion on Gabe. I really like the Half-Life games (excepting Alyx, because I haven't played it) and appreciate a lot of what Steam has to offer (not its current UI, though). So, I really have no opinion or reaction to Gabe's opinion.
All of that said, I can understand why some people are or at least someone would be annoyed by Gabe's statement because I am a little annoyed by Gabe's statement. Again, it doesn't bother me that he prefers one console over another, nor do I care which console that is. It's not him saying that the XSX is better. It's him saying, "Because it is." When I used to teach, one of the hardest things to do was to get students to differentiate between opinions and facts and to be sure they provided supporting evidence or at least argumentation for the latter. "Because it is" is not stating an opinion. It's stating a fact. And, maybe it's true in particular contexts (e.g. raw computational power). Or maybe, unbeknownst to all of us, it's true in every single context. Regardless of which is the case, statements such as these need to be supported with facts/evidence/argumentation/etc.
If I say, "Linux is better" (and you consider me some sort of relative and relevant authority figure), you'll likely ask "why?". If I respond, "because it is", not only is that dismissive (which I think was his intent, if I had to guess), but it's also not terribly helpful. There's a certain amount of condescension in that type of response. If Gabe's answers were born out of a desire of not wanting to be asked the initial question (which dismissiveness and condescension can suggest), he could have said, "I'd rather not answer", "I'm not sure yet", or not gone on a talk show where such a question was a near certainty. Likewise, if Gabe's answers were born out of a desire of not wanting to be asked the follow-up question, he could have answered with supporting facts (e.g. processing power/Game Pass/BC/etc.), supporting opinions (e.g. look/controller/games), "I just like it more", or even "I'd rather not get into that". However, if Gabe's answers were born out of a desire troll people, frustrating academics, rhetoricians, and particular segments of gamers, then I think he answered about as pithily as he could have.