If there was the tiniest shred of evidence that a non-citizen had run then the press absolutely should report it. But there wasn't. Just Trump doing what he does best, which is to repeat a lie often enough that gullible people believe it without realising that they've been manipulated.
Isn't it just the tiniest bit coincidental that the only US president in history who had to produce their long form birth certificate to prove that they were a citizen just happened to be black? Why didn't Trump produce his when he won (or his tax returns as it happens)? Didn't he want to reassure the American people in the same way he insisted Obama did?