I've worked with doctors for almost a decade. There are some great doctors and some not-so-great doctors. Some belong in their profession, others perhaps not. All are smart - you can't get into med school and get licensed without being bright. But, not all have great bedside manners. He sounds like one who's tired of being a doctor.
Here are some facts about practicing medicine today:
1. They're not making much money
They work really long hours, sometimes 7 days/week, have mountains of paperwork, battles with insurance companies, are "on-call" as you experienced through the emergency service, and spend little time with their families. All that, and they make a fraction of what other people would who put in that much time + having close to $300K in debt when leaving med school.
2. Medicine is still as much an art as it is a science.
Anyone who tells you differently has a dark hat over their eyes. They are scientists, but talking to patients, trusting their instincts and making decisions in the patient's best interests is an art.
3. Doctors can be wrong
My OB/GYN dismissed a swollen lymph node on my collarbone as something he wasn't very "excited" about. It ended-up being cancer. Not his fault - he's an OB, not a lymph node specialist. So, I had to trust my instincts and seek another opinion. I had to do the same when my Oncologist recommended radiation therapy after chemo and everyone else said no. 3 other opinions from other lymph experts, and I went against his advice. He wasn't necessarily wrong, but I had to make the decision in my best interest.
It is your job, though, to make sure you understand what's been discussed. I know an Endocrinologist who is originally from Ghana. Though English is his native language, he knows most of his patients here in Indiana don't understand them, so he writes everything they discuss down. If your son's cardiologist doesn't, you need to start doing it for your son to avoid these situations.
5. It's OK to get a new doctor
If you don't like his bedside manner, ask to change to a different cardiologist. Even if you're in Kaiser Permanente, you don't have to see him for your son's cardiac needs.
Good luck. I'm guessing the stress of having an ill son makes your emotions a little more raw, and that's OK. You love him and want to see him well. Be his health advocate! This doctor sounds like he may need to be replaced.