I think there were two moments that turned liberal (to include the media) into crazed loons against the President.
1) His quotes about Mexicans being "rapists." Let's analyze the quote:
"When Mexico sends its people, they're not sending their best."'
He added: "They're sending people that have a lot of problems, and they're bringing those problems with us. They're bringing drugs. They're bringing crime. They're rapists. And some, I assume, are good people."
It's really clear. He's saying some bad people enter the U.S. from Mexico and some of them are rapists.
2) The second turning point was his quotes on the Charlottesville situation. Let's look at what he said:
“Excuse me, they didn’t put themselves down as neo-Nazis, and you had some very bad people in that group. But you also had people that were very fine people on both sides. You had people in that group – excuse me, excuse me, I saw the same pictures you did. You had people in that group that were there to protest the taking down of, to them, a very, very important statue and the renaming of a park from Robert E. Lee to another name.”
After another question at that press conference, Trump became even more explicit:
“I’m not talking about the neo-Nazis and white nationalists because they should be condemned totally.”
It's quite clear what he's saying here.
I believe these two things turned the narrative from somewhat objective to downright hatred towards the POTUS.