I actually wanted to know why do cql onlies said that wwx is morally grey like what gives? Is it because wrh is the supreme of all evil lord in the live action, does it make them think, oh someone needs to defeat this psycho, it's this person! Since this person adopted the long ancient method unearthed by some supreme evil lord psycho, they're morally grey like what? Who's gonna say that now even WRH might be morally grey even if he is supreme lord of evil in cql portrayal is literally in the face? CQL takes are... not it. (No I don't watch cql but I read cql fanfic so I only know of wwx being framed, and yin iron wtf is that. Fuck yin iron)
If you ask me, the whole concept of black, white, and grey morality is somewhat flawed because you're trying to fit into boxes something that's so subjective, that is based on circumstances, societal factors, motivations, and other complex influences. But I understand it is a literary device that's often employed and is considered a valid way to frame characters in the writing community. That aside -
WEI WUXIAN ISN"T MORALLY GREY. He's the very definition of a person who isn't morally grey.
Now, I believe that many fans subscribe to the notion 'the road to hell is paved with good intentions' (while misunderstanding the quote, btw). That means despite WWX's good intentions and righteous ideals, his actions were bad and caused harm. That particular quote is an accurate representation of this situation, I feel. Morality in most religions and spiritual teaching isn't as straightforward.
The quote I've mentioned means that the road to hell is an easy, broad path with wide open gates. The road to heaven is narrow, thorny path, difficult to navigate, and often has consequences. The gate is also very narrow.
Alternatively, it means that just good intentions don't matter, you need to back your intentions with hard, righteous actions. This is, from what I understand the western look at the concept.
Again, fans probably consider this to mean that WWX's good intentions don't matter - his actions and their impact do.
Eastern view also says something similar. Basically, for righteousness, you may have to stand against your society, your family, and countless other forces. The path will be difficult, it will cause harm to yourself and others. Following the right path isn't easy and it can be destructive, violent, and revolutionary. Sometimes you have a large mountain in the path to doing the right thing. You can't move around it and you need to smash it to go ahead. While you may be punished for it in life, you will be rewarded for it after life (entry into heaven, better reincarnation, or ultimately, nirvana)
If you read properly and have a good understanding of characterization, this whole concept becomes very clear. If you don't and focus on surface factors - like CQL-WWX's self-criticism, weeping, and guilt, JC's baseless accusations, JYL's sacrifice being considered WWX's fault, the JZX's death being considered WWX's fault instead of an escalation in a tense, hostile situation, etc.
People who don't actually understand grey morality will immediately label this as grey morality. Thing is, WWX's morality is never in question. He is righteous to the very end. The only situation where he can be considered anywhere remotely grey is during SSC where he goes overboard against the enemy.
Also, a high moral ground is earned. Even if you consider WWX's actions during SSC as morally grey, he earns his 'white' morality with his actions after the war.
so, tl:dr - some fans think WWX's actions and decisions undermine his morality and weaken his character because they lead to harm. They don't think his actions and decisions are because of his righteous morality and sometimes doing what's right has unpleasant consequences for all. LITERALLY - LOOK AT HISTORY.