I'm a fan of what Stipe did, but he has no leg to stand on. I suspect there would be no insta-rematch had he starched DC. He lost. Badly. He can at least win one more fight and then fight for the title (right around when DC retires).
DC is a double champion that has done a ton in the sport, with a record that is basically unassailable. He's also a fan of professional wrestling, so of course he's going to be into the promotion a bit. As much as I like Stipe, the UFC can't work with a guy who mumbles, doesn't want to do media and is sort a stick in the mud. There are guys that pull off humble and get fans. Stipe is definitely humble and chill, but the way he goes about it doesn't get fans.
No problem if Stipe's in it to be a super low-key dude that is kind of the "workmanlike" champion, but yelling on social media at a guy who knocked you silly is a bad look. DC at least admitted, in his dazed stupor, that it wasn't much of a rivalry if he couldn't beat Jon.