To be fair, it's cosmetic surgery on the genitals of an unconsenting person.
Not a single medical authority in the WORLD recommends it. They all admit there's isn't sufficient evidence of medical benefit that warrants the risks and that it is very painful. They all recommend that pain relief must be given (and it usually isn't). Check the American Academy of Pediatrics' statements and the Canadian Pediatric Society.
Most of the men in the whole world are intact. Canada's and UK's rates are extremely low. The US has the highest cutting rate in the world.
Your husband is likely reacting badly because he is not intact. If he admits that circ isn't necessary, he is admitting that it is wrong, and that what was done to him is wrong. Worse yet, it would be admitting that his penis isn't... whole. The greatest perpetuators of male circumcision are circumcised males.
To help convince your hubby (to start), here are a couple links:
Some quotes from Howard Stern on Circumcision:
http://www.sexuallymutilatedchild.org/ster
n.htm
A Penn & Teller Bull#*%& Video on Circumcision:
http://video.yahoo.com/video/play?ei=UTF-8
&b=0&vid=620449
Routine infant female circumcision was legal in the US only 30 years ago.... how do you think people will feel about male circumcision in 30 years?
Did you know that the doctor stimulates an erection (thus, the infant's first sexual experience) in order to approximate how much skin to remove?
Next an object is used to tear the foreskin away from the glans (head) before it is cut off. Did you know that until a child is retractable (avg age 10.5 years), the foreskin is attached to the glans in the same way your fingernail is attached to your finger? Imagine wripping your fingernail off....
Also babies are hypersensitive to pain because they lack the myelin sheath that serves to insulate nerves protecting the body from profound pain - which isn't developed until adulthood.
His body, his penis.
I could go on and on, but can't right now. This has been discussed to death, but the posts are old so aren't seen. There's plenty of information to be found to arm yourself for your next discussion with your hubby. If you have any specific concerns, i.e. if he gives you specific reasons for wanting to mutilate your future son(s) feel free to PM me with a specific question and I would be happy to provide you with information.