Because they aren't attacking him in good faith. It's like the Gina Ortiz thing. They attack Beto for not endorsing formally, but don't think about how she would have gotten destroyed without him on the ticket. Things will go much worse for her in 2020 I'm sure unless Beto is the nominee. Every day I see a new negative headline pop up about Beto. There's one writer from politico that does one negative Beto headline a week it seems like.
It feels like a lot of the media and especially Morning Joe are mad that Beto hasn't been "kissing the ring". He's been more focused on talking to voters than doing the media circuit and sucking up to them, so the media is taking digs at him whenever they can because there's no "relationship" yet. Well that's my theory at least. There are fair criticisms of Beto but a lot of the stuff I'm seeing lately just seems petty.