
It sounds like a dominance thing rather than anything sexual,he is trying to get a higher ranking in the pack and that won't change if he is neutered, but his over all temperament may,vets always advocate them being neutered as it is income for them and in most cases it will not stop the behaviour the castration was done for. My girls as well as the boys hump each other, quite funny when they have a threesome unless you have visitors that don't understand dog behaviour.
We have had several males through childhood and now well into adulthood and never found the need to castrate any of them, they have all died of old age between 13-16yrs old.
I have a mixture now of 2 males and 3 females all intact and will get the females spayed when they retire from breeding but the males will stay intact.
Provided no one is getting hurt then leave them to sort it amongst themselves, if wary then distract him or do time out till he calms down.