I don't care if they're slapping each other's backs and high-fiving! Trump is currently the most powerful person in the world, and has a long and storied history of using that power to harm those who slight him or bruise his fragile ego in any way.

Obama knows this; he's been on the receiving of Trump's petty vindictiveness too many times to count. And he could just as easily be placating Trump so that he doesn't issue an executive order to, say, require every publicly-funded university in the US to offer a "men's rights studies" major, simply out of spite.