Aww, that's great! These poor men, all they ask is for love and hugs and reassurance that they totally rock our world. Lol, I jokingly told my husband not to even worry about the "look like daddy" argument, because, as I put it, I was sure our son would eventually be endowed like daddy, and that matters most
I was being silly, but I think that kind of thing being said out loud is really important. Along the lines of the link mama24-7 gave you, I think husbands really need reassurance that going the intact route is NOT a judgement against their penis... that they are in no way inferior and you are very happy with them just as they are. In my experience, the defense walls start crumbling down then, because that is the root of his argument, even if he never admits it. Actually, I think that is the root of a lot of the arguments against being intact... good old fashioned defensiveness. Since you already have 2 circ'd sons, I think a great way to go about it is "hey, we're all different and nobody's better." No hard feelings needed, no defending on the part of the circ'd or the (hopfully) intact sons needed. I think starting an open conversation about it is great. I found that it was far easier if I didn't "plaster dh to the wall with info" as he so delicately puts my discussion tactics
I just let the conversation flow little by little over time and didn't press for him to actively discuss it unless he wanted to.