I wouldn't give a kid as young as six a firecracker. Maybe a sparkler, outdoors with supervision, but not a firecracker. Fireworks are, in essence, colored explosives, and are in many ways more dangerous than guns. Now, shooting is a fun sport, but I wouldn't take a kid shooting until he/she was at least 10, though I'd start instilling safety at 5 or 6. Fireworks? Even later.

Would you give a six-year-old kid a bucket of black powder and a lighter? If not, why would you give him a firecracker?

__________________
"When in the course of human events it becomes necessary for one people to dissolve the political bands which have connected them with another, and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and Nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation... We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness...."
- The Declaration of Independence