Your analogy, while interesting, does not transfer here. Between you and the lineman, you both were trained in football. Floyd Mayweather has a lifetime of SOME SORT of fight training, even if it's terrible not-well-rounded. Physics, of course, favors Lebron James in all out fighting, but fighting and life is about the skillful, competent application of physics. Lebron James has spent much of his mental and physical energy getting muscle memory for basketball moves and tactics and mental habits and strategies for such. That is a huge detriment working against the utilization of his superior physical assets. Now, Lebron James does have tremendous strength and agility and that will get him somewhere, but it is not a "clear" and "safe" bet like our Letsrun founder, who is venturing into the uncivilized barbarism of fighting speculation, seems to think.
If I were Lebron James I would not risk going into a fight. Why? I guess rojo doesn't seem to understand, if you are not a trained professional fighter, taking hits from a trained professional fighter is a bad idea--life threatening. And there's still caution to be considered even if you are Lebron James' size and ability.
If Lebron James weren't so old, worn out and habituated and accustomed to the trappings of NBA life, and he got a good bit of well-rounded MMA training from the best,
then Mayweather better be absent and have some alibis.
But that is not the case.
There have been MMA matches of very large, former professional sports athletes who turned fighters--and some of whom had success and formidable victories--who lost to significantly smaller fighters. Again, it's not for certain, as big guys demolish smaller guys all the time in the MMA. But it's far from certain that, as Rojo claims, we're stupid for asking the question. Life & limb on the line and that's no joke.