Sonny Boy is sort of about child abuse and the scars it leaves, and is actually very sensitive in that regard. It's also about a town ruled by crime and fear rising up against its oppressive king. Also, there's a country doctor who was disbarred for implanting monkey organs in people. And a massive desert redneck battle at the end. For the most part, though, the movie is indescribable. There are all sorts of weird details, like the table lamps sitting on the local bar; and there are scenes that don't quite end in a logical way. Supposedly, the studio panicked and shut down production in the last week, which is totally plausible. The film had a very abbreviated theatrical run, and I don't think it's had any legitimate home video release. It used to be available via bootleg tapes.
It's actually surprising that it had any theatrical release, and it's a testament to a lost era in exploitation film making. It's certainly not a perfect film, but it's one of the strangest and most original I've seen. You could call Sonny Boy the best movie in its genre, if only because there are no other movies in its genre!
That's David Carradine singing the theme song. I have no idea if he recorded the song in drag.