Well, he didn't have a glass jaw. He only got knocked out by good punchers, or when he was past his best. Williams had great power and different intangibles compared to Bowe, while I disagree with Red Cobra. Bowe would likely give a harder fight then Williams did- Although I still favor Liston.
Sorry i just wanted to demonstrate the hugely significant difference in chins & durability. While Cleveland was likely green (despite being 31-1), he was KO'd in 3 rounds by the 176lb Satterfield, with 2 knockdowns. I also think Bowe may have had more power than Williams, & this would've been evident if he'd faced his opposition...
The same points/arguments could be made about Patterson - maybe Liston simply had his number? Plus Patterson was one of the most maligned HW champs in history - far moreso than Holyfield ever was. In the end, Bowe proved he could be successful against a far higher caliber of opponent than Liston did - making any claim that Liston was simply "a different class of fighter" shaky at best.