Maher gave a platform to Milo Yiannapoulos. For years, he's welcomed Ann Coulter onto his show.
There's no responsibility from who he brings on in terms of pausing to think about who he's giving a microphone to, and if he's legitimizing them.
And in the end, he'll just shrug and say, "Why should I, I'm a comedian," to absolve himself of whoever he invites on, or whatever he says. And I'm not here for that. It's terrible punditry, and really not good political satire, either. He just fails at both.