None of those people are AI theorists so it isn't clear that their opinions should get that much weight given that it is outside their area of expertise (incidentally, I'd be curious what citation you have for the Hawking claim). From the computer scientists I've talked to, the impression I get is that they see AI as such a failure that most of them just aren't bothering to do much in the way of research in it except for narrow purpose machine learning or expert systems. There's also an issue of a sampling bias: the people who think a technology is going to work are generally more loud about that than people who think it won't. For example, a lot of physicists are very skeptical of Tokamak fusion reactors being practical anytime in the next 50 years, but the people who talk about them a lot are the people who think they will be practical.

Note also that nothing in Yoreth's post actually relied on or argued that there won't be moderately smart AI so it doesn't go against what he's said to point out that some experts think there will be very smart AI (although certainly some people on that list, such as Chalmers and Hanson do believe that some form of intelligence explosion like event will occur). Indeed, Yoreth's second argument applies roughly to any level of intelligence. So overall, I don't think the point about those individuals does much to address the argument.