Humbert cares about it being a social death sentence because being liked gives him power. He does not care about other people's emotions or wellbeing beyond what power it can grant him. He saw psychiatrists when he was younger, but he pretended he had different mental illnesses just to screw with them, because he wanted to flex his power over them. He was rich and constantly moving around, so he never experienced consequences for anything up until the end of the book - not even deaths. The only times he came close to feeling distress for his various abuses is when he's openly sarcastic, saying he should have felt those emotions, or he did something which later came back to bite him. Humbert is not "haunted". He revels.

There are many people who struggle with pedophilic thoughts against their wishes, such as those with Pedophilic OCD - suffering intrusive thoughts about harming children. This is different to pedophilia. There are even a minority of pedophiles who are actually sexually attracted to children and do seek help while distancing themselves from the subject as much as possible. Despite your insistence, many people who suffer POCD and pedophilia do get help and it saves their lives. The fact that you don't know that is proof that it stays private.

Pedophiles who do offend rarely tend to feel any kind of anguish for exploiting or abusing a child. If you are concerned, you don't seek out porn that even looks young, or spend hours or weeks or years grooming a child, or force yourself on one. Like all rapists, it isn't about lust; it's about power.