Just thought you should know that cracked me up
I'm so sorry that your parents reacted the way they did. In my opinion is was waaaay out of line. However, people being individuals they are entitled to their opinions
I would play my best dead pan whenever it comes up (especially in a "HOW COULD YOU DO THIS!" manner). It doesn't sound like they're willing to listen to the reasonable side of it, and until the emotional reaction ebbs a bit it may be a futile effort. You seem to be taking it very well and maturely (good on you!!). You're not doing anything illegal, or unsafe, and at the very least they could respect you as an adult doing something you enjoy. They don't have to like it, but this reaction they had is negative to the point of bizarre to me