Because he's not running for their approval. He's running as a candidate and the voters will decide...not the rogue gallery that is watching their influence, as little as it is, dwindle to nothing. You don't have to waste time to refute things that are emotional claims and/or opinions.
Of course he doesn’t have to deal with what some has-been magazine has to say.
Particularly if he cannot deal with their accusations because they are true.
Maybe he will deal with them later but a good time would have been now.