The OP asserting that the pg statement in question was "an astute observation" implies that pg is an impartial observer who is in no way biased by his ties to the startup ecosystem. I disagree with that assertion.
The pg quote that OP provides is very brief -- State/city govt ruling against Tesla/Uber == corruption -- and more an opinion than a true argument because no evidence/elaboration is provided. That Tesla's (very different) situation is equated with Uber's further points to a hastily voiced opinion rather than a reasoned argument. Hence, I would argue that an ad hominem approach is appropriate because there is not much else to go on. Pg voiced an opinion and I made a statement that mentioned some biases that he was likely to have that informed said opinion.