I would definitely continue to talk to your mother about neutering. Show her websites that state some of he health/behavioral problems that unaltered male rabbits can have. Mention that getting him neutered will significantly reduce any odor problems and eliminate spraying. It is, IMO, just as important as having a dog or cat neutered. I have had one altered and one unaltered male rabbit, and if I had it to do over I wouldn't hesitate to neuter the other.

Also, the surgery to alter a male rabbit is inexpensive and noninvasive.

Please please PLEASE convince your mom to do the responsible thing!