DH lost the plot this morning, air turned very deep blue. All because of a bloody stapler! I really don't give a shit, I know what he's like. But DS, who's 9, was genuinely frightened, as was the dog. I think, when there are kids around, you tone it down a bit? It's not on to shout 'Fucking fucking piece of SHIT!!' several times and start banging things about. AIBU?
No of course YANBU. Has he apologised for his ridiculous outburst and for scaring your son?
It's worrying you "know what he's like" if that means he's frequently given to uncontrolled shouting and swearing. It's not okay.
Everyone gets annoyed but impulse control is an important part of being an adult and it's a choice to suck it up and not lose your shit when things don't do your way instead of unleashing a tirade on innocent people nearby.
He didn't apologise exactly, but did reassure DS, who was cowering on my lap, "don't worry, I am angry with the stapler, not you". He does have form for these outbursts, but only with inanimate objects.
I think a lot of it is down to how you handle it. DH occasionally has these outbursts too. I used laugh and tell DC "silly Daddy, he can't get the stapler to work, maybe we should buy him a new one for his birthday".
If you can't have that laugh and joke and then a quiet word to your husband away from your DS then you have a whole other problem going on that needs to be sorted.