Maybe your annoyance (understandable) is part of the point? There are so many things to attack, so many legitimate concerns, that simply calling him weird could spark a little reflection in his supporters and would-be voters, let alone the obvious shock to Trump’s vanity.
It’s not something you can easily deny as a conspiracy theory or fake news or any other excuse about his words and behavior. The man is weird. And psychologically, I think it’s harder to defend a person described that way, or at least makes a defender get a little self-conscious. Trump being deemed weird is really indefensible, and I think it could work in deflating the cult of personality around him.
Not everyone can identify maniacal dictator rhetoric for what it is, and the power dynamic is clearly alluring to Trump supporters. However, knowing a weird person or even being called weird at some point is something almost everyone has experience with. It’s uncomfortable. It makes you ask yourself what it is about a person that makes them weird. I think they’re on to something here. It might give supporters pause and will most definitely give Trump a complex.