He was coerced into having a threesome he didn't want and didn't exactly like almost all of the time, conned into being a sugar daddy, and played by Sunhwa badly that he didn't even question anything despite so many warning signs and red flags. Whenever Mokyeon would drop a hint to anything he'd label him a liar, an abuser, a sociopath, so on. So yes, I will compare the mental maturity and presence of mind a character shows belatedly in the story to a single specific character while conveniently lacking it for the majority of the plot when it came to a certain poorly acting Sunhwa.
It is evident that that what Nanjo cares about most is himself and his own views of things rather than the actual concept of not being gaslit or guilt tripped of coerced. If he feels good about the thing or the person then he wouldn't care, if he doesn't like the person then it's a problem. If he wants to find faults then he will, if he doesn't want to find faults he'll conveniently turn a blind eye to it. Even when he was presented with the truth of Sunhwa, he was still more angry at Mokyeon than Sunhwa and that says a lot.
This in no way erases what Mok did and how he wronged Nanjo, but I find Nanjo's hyper vigilance so very misplaced and odd when he had an out of this situation many times and he chose an in almost every time. It's just ironic.
Exactly, because he liked Sunhwa, and not Mokyeon. You can write as many paragraphs about how much worse Sunhwa is but at the end of the day, he still went back to him and not Mokyeon. He says it himself after Mokyeon confesses the truth, Sunhwa didn’t have that much power over him, so he was going along because he liked him. And he was not even being hyper vigilant with Mokyeon, Mokyeon just acted crazy and no sane person would’ve stayed by his side,

I am happy nanjo can recognize that using death threats is a form of manipulation even if the person using it doesn't have that intention, but it's very funny and ironic how this all-knowing rationale wasn't there when he was being played by Sunhwa and tossed around like a sexdoll in those threesomes. Pretty convenient to gain enlightenment now lmao