I think it just comes down to not understanding it and learning to. Very similar thing happened when I was young and wanted to get multiple face piercings - my mother said she’d disown me, but I did it anyway and she learned to accept and eventually like them in time.
My advice @Edward would be to gather some good (and non-scary) resources to help educate them. Maybe even find some videos of people using them to show them. Give them real-world examples of things like door access at university etc. Tell them it’s the same kind of thing that dogs and cats have. Stay away from videos of injectors and needles unless they specifically want to know how it gets implanted inside you. Be realistic but show them you know what you’re talking about, you’re aware of the risks etc.
I think the trick to things like this is to show them you’re mature and knowledgeable and not just bite back at them. End of the day though, I am an advocate for bodily autonomy so it’s your choice!