Why do boxing fans act like a loss means you are tarnished forever?

I don't know any boxing fans personally who think this, it tends to be Floyd Mayweather fans on this forum.

 

That's the part I hate about boxing.

 

I don't think many posters here really feel that way.
Of course you have some fans here who believe the "0" is sacred, so much even that they don't even want their hero to fight a potential dangerous opponent.
And of course there actually is the "hypejob" factor.
There are boxers who are actually "hyped" for beïng the next big thing, but fight such weak opposition they actually need to keep their unbeaten status to be believable.
If a guy is constantly beating good opposition and he suddenly loses one it's not so big a deal as a guy who's fighting stiffs and suddenly gets beaten by one of them.
There was a huge difference between Dawson losing his "0" and Kirkland losing his "0" for an instance.