I didn't have this issue with my hubby, but we've had other ones. I think our first one was about the way he talked to our son when he was a baby. He spoke in such a curt, direct way and would instruct the baby to "hold still" and other commands. My son didn't respond well to him at all. He genuinely didn't think what he was doing was a concern, potential problem, etc. The hell of it is that my husband baby talks to dogs. All the time. In fact, anytime a warrant had to be served on a house with guard dogs MY hubby was always called to assist because he would be able to baby talk the most obnoxious dogs into submission. So, after bitching at him for a couple of months over the way he would talk to my son, I finally sat down and discussed it with him. I pointed out that he uses baby talk with dogs, but talks to our actual baby the way a drill instructor talks to a recruit and I asked him why. He told me that he hadn't wanted to talk to his son the way he talks to the dog! (picture me smacking myself in the forehead at this point!) I carefully pointed out to him that it's called "baby talk" for a reason . . . and it's because it's the way most people talk to babies. And since it's BABY talk (and not "doggie talk"), it was completely okay to use it with a BABY! Things got better right away.
We've had a couple of other hiccups. I've just found that if I talk to him about why he's doing it, and explain to him about why it might not be the "best" thing - he usually corrects himself.
(The latest one involved the statement "I got kicked in the nuts." My five year old has just started Kindergarten and blurted out that little gem the other day. When I corrected him with the word "privates," my oldest promptly said "but that's what DADDY says!" [sigh] I explained to my hubby that we don't need the Kindergarten teacher calling to discuss Alek's word choices! He agreed!)
It's all a great big learning curve for Daddys. They tend not to have the sensitivity and intuitions that we have. And babies are alien creatures to 'em. You can't just ask them not to do something. You have to provide an explanation about WHY they shouldn't do it. Men tend to be logical and tend to respond better to when an issue is presented logically - rather than to be simply told not to do something.