What if adults treated each other the same way they treat babies? Maybe you already feel as though your boss treats you like a child ... but at least he's not trying to feed you a bottle like the guy in this video. And if he is, you should probably contact your HR department.
Even if your parents (or other adults) don't speak to you in babytalk, there's no way they're perfect. Nobody is, after all.
Here's the reverse situation: little kids talking like old people. We have to admit, this is actually pretty charming. Way better than adults doing babytalk.