I think it requires just as much intellectual honesty to admit that people will make decisions about what they are reading and whether to continue, and some people may include in that criteria whether the person is making ad hominem attacks. The argument here isn't that he doesn't have any useful information, just that the many people are being put off by his presentation of that information.

As for Musk's character and intentions, I think he's been forthcoming in enough interviews[1] as to his reasons for starting his multiple current ventures (Tesla, SpaceX, Solar City). I don't believe his actions have contradicted his words in this respect, so for someone to attribute intentions to him that go against those statements and be believed, the burden of proof is on them.

  [1]: I don't have the links on hand, but he's talked about how after Paypal he didn't *have* to do anything, being wealthy, so decided to focus on a few major areas he thought major contributions to the future of humanity could be made, to his best judgement.  Those being cheap solar power, electric cars, and colonizing other planets.