I don’t disagree with the things you’ve said, but I also think his movies are so attractive because they’re honest in terms of…there’s hate in there, too. There’s a constant oscillation, an internal war, between love and hate. The movies ultimately aim for love, love is always the goal and the hope, and wins out a lot of the time (PDL can even be interpreted as a fantasy, aside from all of the UFOs and curb diving etc., because the out of nowhere over-the-top attraction to a guy like Barry from Lena is so improbable, realistically…), but there are clear moments of earned hate in his movies, from my perspective.
Sydney’s ultimate killing of Jimmy in Hard Eight, Jimmy’s death in Magnolia, the most explicit example being Daniel in There Will Be Blood — that misanthropy is real. There’s a real detest for all Eli represents, the lie, the lie being the opposite of truth, the truth (in a way) being something you could equate with love. It's all the more interesting in Blood because Daniel recognizes the same things in himself, he's not necessarily the moral contrast. The hate usually stems from things that are symbolic of the death of love, agents of change that keep the protagonists from realizing their dreams. There’s an interview with…I think Ben Gazarra, on the Criterion release of The Killing of a Chinese Bookie, that talks about this concept. That the thing in Bookie that motivates Gazarra’s character to carry out the killing he so desperately doesn’t want to participate in is the want to perpetuate his club, “his art”, and that all these people working against that, the gangsters and the money men, were representative to Cassavetes of all of the people who want to “kill the dream.” This movie is a clear, and I'm pretty sure conscious antecedent to Boogie Nights in terms of its themes.
More than that, though, PT’s movies are most honest about self-hate: In Boogie Nights: Jack Horner’s striving not to be the thing he’s ended up as, Amber’s dissociation from the conflict between her roles as performer and mother, Scotty’s whole fiasco, wanting to be wanted as much as Dirk is throughout. Frank TJ Mackey’s run from himself and the past he’s lived through that’s caused him to misdirect his own anger, Lancaster Dodd’s “pigfuck!” reaction to the man who questions him during the auditing of that older woman in the NY apartment comes from a place of being pigeonholed to confront his own lack of truth. Even Daniel Plainview’s self-loathing comes from a conflicted place. He makes small gestures to his son in TWBB, going back and forth between abuse and small acknowledgements of his worth. The love in PT's movies isn't portrayed as the the easy thing to do or a saccharine, end of the universe meaning that's easy to put yourself into if only you decide to free yourself from other emotions (as in a stoner kind of way) -- it has to be strived for, it's a constant struggle to get there, but shown to be worth it in the end.
Edit - was writing this as polka posted. Polka's observation about TWBB being about a misanthrope but the film being empathetic is salient.