How do I convince my parents to get me a tarantula?

I was about to go and get a tarantula when my dad said that I'm not allowed to get it anymore because he found out that if tarantulas are nervous they shoot off hairs and they can blind you so he said if my little brother sees me picking it up then he will think its fine and carry it too, he could do it wrong so my mum and dad said I'm not allowed one anymore, how can I convince them to let me get a tarantula???