Why can't I shave with a Venus razor if I want to?

Okay, I'm a teenaged boy who got sick of the itchy hair on his legs. I was out of razors so I used one of my sister's Venus razors (Unused) and that did the trick perfectly. Worked like a trick. My sister found out and told some of my friends. She said that only girls do that. I told her that if only girls do that, then call me a girl. Now they call me Jenni the Femmy (My real name's Jack). I began to resent them but then I realized that they were the ones missing out on these lovely hairless legs. I began wearing jeans again to stop their mocking but, honestly, Jenni sounds like a way better name than Jack. I've even taken to changing my Messenger name to Jenni thanks to my friends. But they still mock me. So, why can't I shave my legs like I want to? Why is this such a bad thing?