What "every sport fan knows" is meaningless cause most people are goofy followers with no thinking behind their opinions.
To me, with all the GOAT contenders like Silva and JBJ, everything pre-July 2015 is a wash. Machida, OSP, Bonnar, Sonnen, Vitor, Hendo, Irvin, Marquardt, Leben - names who've fought Andy Silva and Jones all popped. And those are just the ones we know for sure. Rampage never popped, despite straight up admitting to being on TRT vs Bader:
https://web.archive.org/web/2013052...-he-used-testosterone-therapy-for-bader-fight
Everything post-USADA is a legit problem, but JJ's only clear pop was vs DC and if you think anyone can make it to the Olympics being clean - I gotta bridge on Mars I can sell you. Add to it, DC was also perfectly willing to leave Stipe in darkness for the rest of his life just to get the HW belt. So selfish cheating isn't above him in any way.
All the significant pre USADA champ reigns are in fact MORE impressive to me cause while there was no USADA to fuck with you, there was also no USADA to protect you from others and their limitless chemical warfare.
So, it's not as clear cut for me. If you pop now after USADA, especially years after the transitioning phase, then it's a smudge on your resume for sure, but I don't discount the achievements that came before it, and only frown slightly at the mess ups during the 2015-2017 rebuild.