You make good points but I'm going to be logical here so please don't go on the attack:
MM beating the shit out of everyone in his weight class doesn't necessarily prove that he is great.
Logically, one could just as easily say those guys are just average fighters, maybe they are great at one or two things that comprise what mma is but they are all just average.
Ali beat great fighters
Fedor beat great fighters
Who are the great fighters Demetrious has beaten?
This is pretty much the reason people exclude Tyson from consideration as one of the greats. It's all just idle fan-talk because he's demolished everyone he has had to but if we are going to engage in idle fan-talk then we ought to be objective imo.
I'll give 2 names in rebuttal.... Ronda Rousey and Chuck Liddell.
Ronda was/still is (in some circles) considered the WMMA GOAT, even though when she was on top of the world, WMMA didn't have top level talent.
Chuck (up until JBJ's initial run) was considered the LHW GOAT when he was a decent wrestler/great counter puncher who dominated wrestlers with shitty standup.
My point is, you can't penalize the fighter for the talent pool in their division. That said, globally there are PHENOMENAL fighters in the 125 division, hell the UFC has a lot of them... DJ just makes everyone he faces look very pedestrian an rookie like.
Saying that the only way a fighter can legitimize themself is to go up and face heavier guys is ridiculous, there are weight classes for a reason. A fighter doesn't necessarily have to be better to KO a guy, especially if he carries a weight advantage. All fighters get hit, declaring that a fighter has to see how he holds up to the strikes of a heavier guy to legitimize his greatness is a insult to our fighters.
Final point (and BTW, this isn't all directed at you, but a general discussion started by a talk point you mentioned).. the idea that DJ ducked TJ has to stop. He stated that he (DJ) wanted to beat the last challenge in his own division, allow TJ to fight Cody, THEN fight the winner in a super fight...... That's a solid personal business decision to make as much money as he can. In a time when many of us are rallying for fighters to get paid more, how can we hate on that sound logical business decision? Just because it ruined one of Dana's PPV ideas (because other fighters had dropped out, and he wanted a big headliner), all of a sudden, DJ is ducking challengers. That narrative has to stop... Fuck Dana White, pussy ass bitch deserves to get his steroid using, cocaine abusing head bashed in.
DJ is the GOAT