DH overreacting or am I really uncaring?

[TheFancyLion]

Teen DS first day back at school, due to snow has his friend coming to the house at 7.30am so they can walk together, friend arrives and DS isnt quite ready (just few minutes).
Our dog starts going crazy because of the knock on the door, DH starts shouting and has a go at DS for not being ready in time because its disturbed him sitting down to have his breakfast.
I try to diffuse the shouting by telling DH that DS hasent done too bad because he was almost ready (which is very unusual for him) and DH accuses me of "not giving a s*it about his feelings".

Ive apologised and explained that I dont like to see him stressed out and that I felt like it was an overreaction to the situation and could have been a conversation rather than a load of shouting. (DS is a bit lazy at times and timekeeping is something of a challenge in our family but i dont believe shouting is the answer).
But now im wondering if AIBU to have called him out about it or whether i should have been on his side about it more?

Side note, this scenario happens occasionally, where DH will get super stressed and shouty about what I believe to be a minor event with DS, I'll try to diffuse the situation, and DH accuses me of not caring about his feelings.

Oh no not at all, so the dog still will have barked.
But if DS would have been coming down the stairs ready then its likely DH wouldnt have had a go at him.

The issue for me is that DH was on his way down, it was literally about 7.32am, so not like 10, 15 minutes. And I felt that DS had done pretty well for his first day back at school after holidays (we all know its a challenge for teenagers after 2 weeks of late nights and minimal rules). So it annoyed me that DH got so wound up and had a go at him for what in the grand scheme of things was a couple of minutes.

I think my question is on whether I should have spoke up at all, as I didnt agree with it, or was I not considering DH and providing him with moral support for DS not being ready on time?

He has form.
He needs firmly telling you will not tolerate him irrationally verbally abusing your son.

Because he needs telling.
Do not ignore it.

Yes precisely what I mentioned above. Bad enough this poor boy started his school day with his bully of a father yelling at him for being 2 minutes late and freaking out over his dog doing dog like behaviour like barking at the door going, but he also put this friend in a very uncomfortable situation to stand and bear witness to his outburst. Really really shite parenting from your DH. I would not tolerate this behaviour from my child’s father ever.