I don't have much to offer in this. My parents have been pretty accepting of everything in our home. They started with very strict limits on number of and size. . . then it got breached on the size limits when I got my BCI. . . Ever since then it has been the one snake my mom has hated the most. . . I've pulled him out, let her pet him, understand who and what he is, but all she sees is 7 ft of muscle that will kill me one day. . .
I will say this though. Things can change. While I was out in Hawaii, my mom was taking care of my collection. She will work with any of the animals python wise, balls, Carpets, and yes, even the burmese. But the Boa she said was the limit. . . During my time away, Bubba spilled his water. She told me the story of her walking by the enclosure and seeing him look so sad that his water has spilled (doesn't happen often, but sometimes he knocks it over). Since this was on day 2 of my trip, she got over her fear and opened the cage on her own account, pulled out the turned over bowl, and cleaned it / filled it with fresh water. When she put her hands back in the cage the boa "bowed to her" as she gave it the water back . . . Since then, she seems to fear it much much less and has become accepting of it. I know this is probably a rare case of parents and snakes, but there is always hope. Make sure your parents realize how deep your passions are for what you believe with your snakes. Make sure they understand its basically a hairless cat with no legs. . . Since the situation is hard to analyze from an outsiders point of view, this is all probably moot, but hopefully it finds some ease to your mind.