You poor thing :((
Just a thought, could he actually be overtired at bedtime, which for some kids gets them "wired" and unable to lay still and go to sleep? TV or video games can give a "wired" effect as well, so stopping them before dinner for the night is helpful.
Not sure how long his bedtime routine is taking, but if it's longer than an hour long from his bath to going to bed it's too long, might be time to tweak it. It sounds like maybe instead of being the relaxing routine to him that you want it to be it's entertainment time, hence he gets 'hostile and wired' when it's time to sleep. The routine is to get him relaxed, everything should be quieting and slowing down preparing him to go to sleep.
Get a dimmer for his room so the lights are low while reading and you can turn them dimmed almost all the way down for him to go to sleep or off when you leave the room. Speak in "quiet" voices only after dinner and while reading, don't sing anything but quiet songs, or do the singing while he bathes. Rub him down with baby nighttime lotion to help him relax.
He's old enough to understand that he gets into bed and stays there, whether he's asleep or not. He can lay there quietly until sleep comes, getting up is not allowed (it "disturbs everyone else who's sleeping and isn't fair to them") except once for potty (allow him to have a sport bottle with water by his bed to nip that excuse.) Get him a cool nightlight so he can see constellations on his ceiling while laying in bed, this one stays lit about 45 minutes:
http://www.amazon.com/Cloud-Twilight-Constellation-Night-...
Tell him he's a big boy now that he's in kindergarten and needs his sleep so he can do everything at school. I honestly think as the year progresses he'll be more involved in school and will settle down some, I hope so for your sake!