I'm annoyed by spoilers. I can't always get to the midnight premiere of a film. I don't live in a time zone that allows me to watch a program the first time it's shown. Heck, here in the states, Downton Abbey Season Four hasn't even started yet.
I think this is a lot like the people who share news stories that are accompanied by graphic photos but neglect to hide the photo. Are they trying to traumatize a particular person in their feed? No. It's unlikely that they are doing it AT anyone. However, it is pretty oblivious. In some cases, so oblivious that it's tough to imagine someone not knowing better. (I'm thinking of a "shared" story that had an accompanying photo that was incredibly upsetting.)
This guy is way out of line for his tantrum, but your hubby did mess up. In the grand scheme of things, it's a fairly small faux pas. Think of it like talking about a party that someone isn't invited to in front of them. I think your husband should apologize and ask for an apology of his own. I know guys aren't really into the whole feelings thing, but maybe something like, "Hey, I'm sorry that I gave away the ending of the show last night. My bad, and I'll do my best to remember not to in the future. But saying that I did it on purpose/calling me a buttmunch? Not cool, man."