One day people will stop chalking up everything Trump says to just be another Trumpish. He suggested a foreign government hack his political rivals, and then what do you know? DNC campaign gets hacked. Granted, it might have happened before Trump opened his mouth, but the news come out at a rather apropos time.
Now Trump is saying someone should assassinate his political rival? I'd be concerned about that a bit more than just "Oh, it's just Trump saying bullshit." We've seen Trump supporters are not right in their heads.
Yet, if Hillary sneezes the wrong way or falls up a flights of stairs (Which every fucking person in the world has done), she suddenly has mental damage and her health is being brought into question.