As easy as it is for Trump loyalists to shout "omg withholding intel from the President is treason," it's not if there's reason to believe that the President might relay that intel to Russia, knowingly or carelessly. And that's the sad part about Trump -- while it's doubtful that he's a Russian mole, he's at least sympathetic to the point where he might discuss secrets without realizing the damage he's doing.
I should stress that I'm taking this with a grain of salt, since the Observer isn't the same as, say, the New York Times or Washington Post. However, this is definitely the leakiest administration in recent history... and combined with the Mar-a-Lago dinner gaffe and the Flynn scandal, it paints a pretty consistent picture.