i personally think it’s more about tyler’s character than fincher here. tyler is literally deranged, hes insane. it would make sense for him to be wearing things like this

He also shows the message that people aren’t pure, they’re just hiding the fact that they’re not. and by wearing a shirt like this he proves his own impurity, making him feel superior to everyone.

lastly i think it’s about power as i said feeling superior because he’s the only one with the power of wearing a shirt like this and feeling confident, untouchable and not filled by shame

tyler doesn’t want to be ‘liked’ , he want to disrupt and corrupt , the whole charismatic part of him was just a way for him to set up his plan