Ohhh, I don't think it's a "fact" that you can't convince a snake-hater to allow once in the house. But it IS more difficult to do. My husband doesn't like snakes either....but now I have five.
It takes a great deal of time, patience, and RESPECT for the other person's point of view. But it can be done.
Without any whining or other immature attitudes....explain to him how quiet and unobtrusive a snake is as a pet. Explain that he will NEVER even see the snake if he doesn't want to. Demonstrate your ability to keep it secured, and your ability to financially care for it without causing him any grief about it. If you have to ask him for money to buy rodents...well....that wouldn't go over too well.
Again, be patient and mature about the whole thing. You may not get a "yes" answer anytime soon...but over time, if you can show that your interest is sincere and steadfast (without pestering him!)...he may decide that it's ok to have one.