Defiantly not. Airsoft guns are not toys. You can probably kill someone with it if you shoot someone at point blank range, depending on the gun. Or you can go blind, lose and eye... a lot of things can happen. One of my friends painted his red tip black one night when he was "high" and went into a convenient store and tried robbing it. He was arrested for second degree assault, second degree burglary and charged with felony crimes. I don't think you should get a 9 year old an airsoft gun.
No I don't believe a child should have any type of guns at all...if you watch the news and read the newspapers that should explain why children should not have guns period.
What does the child want to use it for? If it is just to have it and for fun I would say no. If it is just for shooting practice with specific boundaries and rules (like only can use while supervised and only to shoot at these pop cans set up in this certain place) then i would say it is fine