Why do parents over react?

I'm 14 years old and hv been dating someone for six mnths. My parents are very protective over me. They found out that me and my boyfriend are making out and they took my cell phone away and they said I cnt ever see him again. I want to tell them tht this isn't right and they are over reacting but I want to say it nice and respectful so they won't get anymore mad. Heeellpp mee!! Please get back to me as soon as anyone can! Thank you. Any advice would help.