As an owner of two airsoft guns, one of which has been upgraded, I can see the arguments for and against.
For starters, a proper airsoft gun (not some £10 spring-loader you got off a market) is not a toy and not to be "messed around with". Sure they are not exactly lethal but can still put eyes out and/or cause serious injury.
I suppose I am in a good position in that I was taught respect for, and safe handling of, live firearms when I was an Air Cadet. Airsofting got a lot of negative press but has taken massive steps to allay many fears and long may it continue.
These days you need to prove you're a serious airsofter to buy the guns and I think that's a good idea (even though I don't currently qualify) because it thins out the dickheads. The allure of airsoft weapons is obvious in that they look, and operate, pretty much exactly as their live equivalents. This does wonders for the immersion but it also has a dark side in that, if someone pointed an airsoft gun at you, you'd be hard-pressed to tell if it was real or fake, especially in the UK where there is no stipulation that you paint the barrel orange.
Like a real gun, an airsoft gun is no danger to anyone until it gets into the hands of a fuckwit.
Wardy
PS I recall a bunch of knobbers claiming that airsoft guns could be modified to fire real bullets. Seeing as my Beretta M92FS is a 6mm calibre (real calibre 9mm) and my M4 6mm also (as opposed to 5.56mm in the real world) this is pretty unlikely. They finally shut up and went away when it was also pointed out that attempting to fire a live round in an airsoft gun, even one that is 'metalclad' would most likely blow the gun to bits!