Some thoughts:
1. The black belt found in the friends car...
I don't think this anything to do with erotic asphyxiation, in fact I'm positive the belt has nothing to do with that. Erotic asphyxiation is usually accomplished using hands not objects, esp in a place like a public park or some other public location.
So where did the belt come from?
Perhaps Blaze was wearing it and it was either taken off as part of the sexual act for better "access" or it was removed to make it easier to place a body, perhaps place a body in a plastic tub to move it in the darkness? Fellow gents will be familiar with what I'm talking about, it's damn near impossible to bend over if you're wearing a belt. OR...the driver was wearing the belt and he took it off to make it easier to undue his pants OR he simply had a belt in his car.
2. The camping gear...
We're all freaking out about the camping gear with no point of reference. Perhaps the gear was in the car because the driver was either planning a camping trip or had recently returned from an overnight camping trip. I've learned with my nieces and nephews (who range in age from 18-30) that kids today will take impromptu "camping" trips but it isn't camping in the normal sense, they will go somewhere for two or three nights, usually either a music festival or just hanging out with friends and they're not going into actual wilderness situations, more like organized campgrounds or state forests no further then maybe 30min from a town. These kids aren't outdoorsy types in the least, they are a lot like Blaze, they come from middle class/upper middle class families who live in metropolitan areas. I think the camping gear is nothing but an excuse for LE to use in their getting a warrant. Remember, LE will use the presence of a ham sandwich in the home if it suits their purposes even though they know it has no actual connection to a case.
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4. The motive...
I'm getting an accidental death or murder in the heat of the moment vibe from this case. Some of us are coming from a place of serial killers and other garden variety crazies, this is more than likely a 19yo rich kid who went to some artsy high school in California. This kid is not some gang banger from Compton or a pig farmer that feeds prostitutes to his livestock in the boondocks of Canada. He isn't street smart, he has no clue what he's doing. I would speculate the closest he's been to a previous interaction with the cops is a traffic stop.
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6. The "fight club"...
There is no fight club, period. It's an excuse made by the driver to explain the scratches on his hands, end of story.