Here is exactly why Trump continues to be popular:

In an interview that will air Sunday on “This Week,” ABC News Chief Anchor George Stephanopoulos asked Vice President Mike Pence whether it was appropriate for the president to question the legitimacy of a federal judge by referring to him in a tweet as a “so-called judge.”

The words of an ABC post.  

The Press,  when it suits its purposes,  has decided to push forward its "politically correct" standards in the case of the activist judge who challenged the President.  Of course, the Press was not so congenial with the High Court when it ruled in favor of Citizens United,  but that is a point of Democrat hypocrisy  for another day.    

More to the point is this:  Trump thinks and speaks like the blue collar world he represents   . . . . .   all 70 - 80 million of them in this country.  His tweet criticizing the "so-called judge" is exactly what Middle America might say.  As a result,  his tweet struck a cord with the folks and did so immediately.  He is not picking a fight with the Courts.  We are already so engaged.  Rather,  he is identifying his stance with his voting base,  and  with each similar action,  is growing that base.