Mojo and mcfarm both have idiosyncrasies about Donald Trump. One can see no good, and the other can see no bad. The trouble is most of the Forumites agree.
An idiosyncrasy is an unusual feature of a person (though there are also other uses, see below). It can also mean an odd habit. The term is often used to express eccentricity or peculiarity. A synonym may be "quirk".