Generally because people are looking solely at the planes and ignoring everything else that is essential for the planes to operate, like adequate crew training, basing, maintenance, logistical support, and so-on and so-forth. The consistent analysis across a broad array of scholarship, up too and including strategic air command at the time, was that these issues were crippling and would (and did, in fact) take a significant amount of time to overcome, although admittedly in a long-war there is also no doubt that the US would have that time. The focus on the specifications of the aircraft themselves is hence something of a red-herring.
The sense I'm getting is that the denialism over this is fundamentally a result of nationalistic sentiment of the "American Exceptionalism" variety. It's not enough that the US would win such a war. It also has to win painlessly and effortlessly because for it to be otherwise means the US isn't as Exceptional as their world view holds it to be. For the case of a late-1940s WW3, that requires an idealization of SAC's capabilities which tries to pretend the myriad of issues that were afflicting it don't matter and a downplaying of the USSR's capabilities to the point that it comes off as less of the military superpower it actually was and more a cartoonish strawman.
And when someone comes along and points out that, hey, issues like a lack of training, maintenance, and prepared forward bases actually matter and hey, here are sources which say the Soviets have set-up a effective air defense system that would be a up-hill struggle for SAC when combined with all of the aforementioned issues... well, that offends them because they view it not as an analysis of reality and an attack on their world view. So when all their attempts at dismissal are debunked by actual analysis, they start resorting to the sort of fallacies we see Marathag has been resorting too.