This is just an opinion on a trope from me being an overthinker and an angst lover.
I don't actually particularly like the no nuance, ghost fighting equals friendship thing, especially on Danny's end.
For one, on the comedic end this usually results in the loss of autonomy and "joking" victim blaming on Danny's end. The infantilization, even if Danny is objectively in a better place for it, urks me somewhat.
On the more serious side, if you take into account the original motivations of many of the ghosts and their actions, a lot of them are still pretty unforgivable.
Vlad continually targeting Danny and his mother is not cured by calling it an obsession.
Skulker hunting him in revenge for saving an animal from him isn't really suddenly acceptable.
The multiple mind control ghost incidents, including Ember, aren't really suddenly acceptable. Ember and Dora both use mind control in a way that would have resulted in SA of a compromised party.
Walker looks even more like a power hungry bully.
Johnny 13 seduced Danny's sister under false pretenses, and tried to use her as a meatsuit for his girlfriend. If he had succeeded, he would have, at best, been a murder, and at worst, indirectly assaulted a helpless Jazz.
You have to heavily rewrite everyone's initial encounters to make the headcanon make sense.
Even then, if Danny isn't aware of the real reasons his human life is being ruined, he's perfectly justified in still hating every single one of them.