Unaltered males have INCREASED chances of testicular cancer and unaltered females have a HIGHER chance of breast/uterine/cervical cancers even if they only go thru one heat cycle.
Spaying and neutering your pet is the RESPONSIBLE thing to do UNLESS you are a licensed
breeder. If you think that those of us who spay or neuter our dogs "outta think again" I suggest you LOOK IN THE MIRROR. I have a feeling that your reservations about neutering your MALE bunny is b/c you feel YOUR manhood is threatened.
WHY SPAY?? Dog Fancy Magazine February 2000
AN UNSPAYED FEMALE DOG, HER MATE AND ALL OF THEIR PUPPIES, IF NON ARE NEVER NEUTERED OR SPAYED, ADD UP TO:
1 YEAR = 16
2 YEARS = 128
3 YEARS = 512
4 YEARS = 2,048
5 YEARS = 12,288
6 YEARS = 67,000

and
Bunnies and cats go into heat more often than dogs and can have larger litters.
I never thought much about neutering/spaying animals until I realized how many pets are put to sleep every day b/c of people that can't be bothered to get their pet fixed, or that it is unnatural to alter them. And Bunnies are the 3rd most likely animal to be found in shelters right after dogs and cats. Of course unless you get another bunny you don't have to worry about HIM reproducing, but for you sanity, it sounds like it would be a good idea.