Because it helps to inoculate President elect Trump. If SNL decreases their attack skits Donald Trump's tweet has been effective. If SNL steps up their attacks they further prove his point and a lot of people will say you know what D.T. was right they are over the top with their attacks. If they change to more light hearted poking fun at D.T. then he wins because it will make him more popular and keep him in the public eye even more.
The other problem the press is having is that D.T. follows a Hollywood maxim that any publicity is good publicity. Just think a one line tweet nets Kelly Ann Conway a segment on CNN. D.T. is a 10th degree black belt in Media Judo. No matter how hard they attack he is able to use their own force against them.
:: a 10th degree black belt in Media Judo. No matter how hard they attack he is able to use their own force against them ::
That is more appropriately considered, “jiu jit-su”