Why does my husband kiss terribly, but won’t let me help him get better or show him what I like?

I think you're right and it's male pride. Since he's a man he thinks he needs to figure it out for himself. That's unfortunate because you could help him since you know what you like and what would work better.

One wonders why after two or more years of this bad kissing you chose to marry this man.

Sounds a bit like you didn't handle the issue very diplomatically.

It probably put-him-down and embarrassed him -- just really got to him - because it's like telling him that he does not know how to kiss (very personal thing).

It is pride - and a male thing (would be for a woman, too) - and it may have been coming on too strong to him (destroyed his self esteem).

Probably a little of both. We'd like to think we can tell our spouses anything, but that doesn't mean it doesn't hurt the ego to hear it. You don't say how long you're married or how long you were together before, but he probably was always a bad kisser and you just accepted it. Which is why it's hard for him to hear that you now suddenly (in his view) have a problem with it.