The simple explanation is what defines a real man? It’s the same as saying you throw like a girl, it’s never used as a compliment. It may be used as an expression in jest or for fun but other times it’s used as a put down.
Goes back to real men don’t cry/show emotions etc.
They played exactly on those thoughts you suggest the race walker is inadequate and not a “real man” emphasise the point by exaggerating the clothing and then suggest a snickers can cure all that. The previous ads with angry celebs was actually quite funny. That one isn’t really.
(the other way of looking at it would be along the lines of the current ranks of politician’s who think things like being gay can be cured)