This "wearing nappies" thing is most likely temporary. For me, I never got night time continence and I just wear condom catheters when I sleep. No big deal.
It is a VERY SHORT time (a few months or so) in the relative scheme of things. He needs to understand that and get over it. If he had stitches for a cut on his arm would he stare at it and get upset that it isn't healing in minutes? Of course not.
This is similar. He has to wear the protection at night because he had SURGERY! Not because he is a little child that hasn't been potty trained. In time (same as a healing wound), he won't need it any more. VERY, VERY, VERY small price to pay to be cancer free in my humble opinion.
Either he didn't listen or his doctor did a lousy job of setting expectations. You don't just get continence in a few weeks. He's pretty darn lucky that he's got any daytime control at this point. Most of us didn't and once we found out how long to expect it to take, most of us stopped worrying about it and just on with the business of healing.
Maybe it's time to whack him upside the head and remind him of what he does have. He has you, your children and whole hell of a lot more time to enjoy all of your company. Seems like a reasonable trade off for a short time of having to use nappies!