ooh gillybob that's awful, you said they were old, 'old farts' and 'silly old bugger' when he put his fists up, could he have dementia or something ?
I'm only thinking same as you, that this was an extreme over reaction to a mistake. I think this is a situation for your daughter to try to put right. No matter of right or wrong or how unreasonable they were it won't get better without trying. Perhaps if she knocks at their door with an apology for not asking first, give them an opportunity at least to apologise for their part. They may have felt very upset over it themselves and aren't sure how to approach her. If they are elderly as you say then maybe they feel vulnerable or have cognitive problems such as dementia, or they could just be and always have been belligerent people. You will never know unless your daughter goes and knocks on their door and tries. First steps are difficult but I think on this occasion it's best to give them an opportunity to repair some bridges as neighbours. Good luck to all of you on this one