That's not really an ad hominem, it's a criticism of the manner by which Elon (according to the commenter) goes about trying to achieve his objectives.
You can disagree with that characterization or interpretation, but it's not an ad hominem because it's the main subject matter in this context.
Ok, but is there actual evidence of Elon Musk behaving in a racist or sexist way? Because if not then this is just a generic attack on the man, not an attack on his ideas.
There are allegations (probably in the form of guilt by association), vaguely suggestive tweets (or tweets that have obvious potential for misinterpretation), and things like that.
I think you could make a very good case against that comment, but "ad hominem" isn't it IMO. I'd argue {{citation needed}}, "lacks substantiation", "slightly hyperbolic", or something like that.
Gish Gallop isn’t a logical fallacy, it is a debate tactic. Seriously people, if you’re going to call out misuse of logical fallacies, make sure it is one.
You can disagree with that characterization or interpretation, but it's not an ad hominem because it's the main subject matter in this context.