What reasons are given for calling him an illegitimate President by some people?
Uh, we're talking about him being an illegimate President for a lot of reasons, including interference by Russia, Assange, the FBI, the fact that he didn't win the popular vote, the fact that he's a pathological liar--including lying about Presudent Obama and Clinton--he's a sexual predator, cheat, fraud, and on and on.