An ad hominem call is often a logical fallacy, as in many cases the person can be a very key point in the argument.

If some one is running for president for example then his personal views and life experience can and should be brought into question regardless of what his says in his speeches.

This case isn't different, he isn't talking about global warming he is talking about founding and funding a new company so his past, and current troubles are very much material to the debate and cannot and should not be thrown aside because it might appear to to be an ad hominem.