You're 18, which means your AV'd, so who gives a f--k. Go buy AS guns.
Also your dad is being a bit paranoid. I also work for the Government -for the Corporate Security Branch at that- and I have a ton of airsoft guns. I fail to see what "working for the Government" has to do with anything. People on this forum are lawyers, police, firefighters, retail sales people, bums, you name it.. we have it.
There is nothing illegal about airsoft. Sounds like your parents are suffering from "big scary gun" syndrome, also known as "being detached from logic and reality" syndrome.
"Someone in a Prius tried to race me at a stop sign the other day. I couldn't believe it. I had him for the first 100 feet or so but I can only walk so fast."