He didn't call him "Mr. Magoo". There was a report in a left leaning newspaper based on a anonymous source that he called him "Mr. Magoo". Here's the CNN report:
The Post, citing people to whom Trump has spoken, said the President has complained about Sessions not defending him and not being loyal enough, comparing Sessions unfavorably with lawyers who have worked for him personally, and had called Sessions "Mr. Magoo."
People whom "Trump has spoken" to could be literally ANYONE. Two leftists that Trump "spoke" to could have colluded and SAID that Trump called Sessions Mr. Magoo. The point is that this is fake news designed to divide the opposition to the left.
When you cite leftist news as reality you're carrying their water.
Sessions is a myopic AG.
Well then...never mind. /s