It seems that the new President of the United States is happiest when he has an enemy to attack. His fans also love this pugilism, perhaps because this is the feeling of being in the thick of it together, us against them.
'Them' in this case is the mainstream media in America, mainly the big outlets such as the New York Times, The Washington Post, and CNN.
It suits Trump to berate the media, because mainstream news was quick to point out his inaccuracies, contradictions and falsehoods during his election campaign.
Almost all of Trump's rallies were an opportunity to attack the media. "I would never kill them, but I do hate them. And some of them are such lying, disgusting people." This was Trump's opinion about journalists at one of his campaign rallies.