I think it's pure shock. The professionals don't seem to realise just how much depression sets in after heart surgery. Your husband is probably just hanging in there with the death word circling around in his head and really doesn't know how to deal with it. I had a triple bypass in 2007 which collapsed after just 3 months, and it's likely your husband has heard such stories which doesn't give much confidence. Is he aware that even if he develops more blockages, they will very likely be able to deal with them using stents? is he aware that he is not at the end of the road and has as much chance of living a good life as anyone else? I agree with Ireneo, he needs to speak to others in the same position, and see how well they are coping. I met people who were stented over 10 years ago and are still going strong. It can be a real confidence booster. You start to realise that each day is a blessing, the same as it is with anyone on the planet, and nobody knows when their number is up. Once you get that in your head, you are on a home run. If he won't listen to you, call his Doctor who can phone him to make an appointment, keeping you out of the loop to begin with.
I'm sure you know that although he is being nasty, he's doing it because he's scared stiff inside. For many people, having a bypass is like you've been told you don't have long. A good Doctor will put him on the right path.
Did he attend any cardiac rehab classes? Those can be quite helpful in helping a heart patient (whether heart attack or surgery) regain the confidence they need to live life fully again. Some people have a lingering fear that if they do too much activity, even sexual, that they may damage their heart. Or they feel some depression that they're not "whole" any more and they somehow lose value as a person. I'm not sure if you're husband has said anything to this effect and he may not. It may be a thing he is struggling with inside and won't admit.