I mean, I like sp games a lot more than MMO's, but yeah, he hasn't given a single good reason why they're better. I mean, this is about as shitty as an editorial can get.
Maybe I can try, at least as far as it applies to me. For me to really enjoy a game, I have to be fully invested in the world that exists in that game, or absolutely engrossed by the gameplay offered. I can't be invested in the worlds of MMOs; because while they are expansive and detailed, they go on without me and often have other players doing things which remind me of the outside world. And I have yet to find an MMO where the gameplay is satisfying enough to keep me interested for more than a month. I also don't generally play any multiplayer games of any kind unless I can play them with someone I know. I own two copies of Left 4 Dead, but I rarely play it. It's still one of my favorites, I just don't play it very often because somehow most of my friends didn't buy it.