Well, the diversity line is PC bull$hit. Real diversity to any of our major cities would be Republican Mayors. As far as I know about Dallas, it has only had 1 GOP Mayor in a century, and that was former Congressman Steve Bartlett who served a single term from 1991-95. Electing another rodent is merely business as usual, whether they pack fudge, eat clams, or whatever else.
Dallas, like all TX cities, does not elect mayors according to party. They are all officially nonpartisan. There was a nominally Republican mayor in the 1960s named Eric Jonsson (not sure of the spelling).