Interesting stuff. I guess there isn't much that can be done there... At least a neutered animal can't have offspring. That's the main thing besides spraying the house. As long as those two things are taken care of, one can afford to laugh at him humping a few toys and other cats.
Whuh? I'm confused! Can men get desexed and still experience that sex urge?
It happens. Male neutered cats, especially but not only those who have experience with sex before being neutered, will go through sexual behaviors.
One of ours has frequent relations with my stuffed animals if they are within his reach :) and will get confused and worked up if exposed to a female in heat (this doesn't happen frequently, but it has occured). It's perfectly normal.
I suspect that there is just leftover testosterone in their systems.
BTW, it happens with people, too. I've read stories about eunuchs, centuries ago, who had sex lives. Like with our cats, it wasn't the same, but.... :)
I agree with MJ. It may be a display of dominance.
Could he still have some leftover "male instincts"?
Our two males get into fights. Both are neutered, but sometimes Sahib gets on top of Waldo and pin him down. Probably a display of dominance in our case.