Some people blow up, and then are fine a couple of days later; it's the stereotypically 'male' fighting style, but I've not noticed it to be gender correlated all the time. Your husband and his friend will probably get over it on their own, and someone else jumping in will only prolong it. If this is a repeated pattern, where the friend regularly verbally abuses your husband who doesn't like it but won't say anything, I'd give different advice. But if he genuinely doesn't care, it's up to him to not care.
I think the friend is being ridiculous to keep it going publicly; an apology might help but if your husband genuinely doesn't feel he did anything wrong, I can see why it might be hard for him to want to do that.
Spoilers are so weird. Sometimes it's seen as evil to say anything at all about something on the internet, but last year there was a certain Game of Thrones episode where spoilers were *everywhere* right after it aired and it would've been pretty much impossible to go online and not see them. I think it would've been unrealistic to tell people to stop at that point, and people obviously had a great time talking about it in a way that would've been lessened by having to wait...so, I don't know what the answer is.