I've known some unfortunate people with that syndrome, and I saw no signs that he had it. A few ticcish habits, sure . . . but full blown de la Tourette's is no joke.
Bush's lip curling and facial tics were the source of the cartoons, as with his tendency for verbal gaffes and humorous neologisms ("strategery"). Haven't heard any direct information on the diagnosis. His mother talked about some kind of reading issue, as a child.
Liberals did not complain much when Bush was likened to a chimp in political cartoons. Maybe that's the difference.