How do you load him? And how do you manage the disrespectfull behaviour when he refuses to load?
horse are simple creatures. they like comfort. They dislike discomfort/irritation.
So make outside the float uncomfortable, and inside the float comfortable. No don't use food. This trains nothing.
Whether the discomfort be via putting the horse to work when it is outside the float, and as soon as it walk towards the float take all pressure away. My discomfort of preference that has worked with every horse I've floated, has been with a stiff dressage whip or long piece of polypipe. Tap the horse on the hindquarters/hind legs continuously and fairly firmly no matter what he does (kicking, bucking, rearing, striking, backing away- backing away = harder, faster tapping - etc.) and as soon as he takes even ONE step towards the float, take the pressure off, pat and reward, then ask for another step by gently putting forward pressure on the halter. If horse doesn't move forward, go back to tapping.
It does take a while, you need to be very patient and work on it every day (short sessions 3 times are day are the best way to go) until the horse will figure out that it is bloody uncomfortable standing outside getting tapped, but inside I get nothing but pats and comfort.
My retired welsh pony used to be an absolute horror to load. When i first got her we had to get the vet out to sedate her to get her in (I know, dangerous but we knew nothing about horses, I was only 10!!). Sent her to a trainer who used the tapping method (in fact he was the one who taught me how to use it), and this pony will self load EVERY time even after years of not being floated. I use her for other horses that panic inside the float as she's just so calm about the whole process.