I am an AIBU virgin, so please be kind
Apologies this is so long.
This happened over two weeks ago, but whenever I think about it I feel really guilty that I just stood and did nothing, and I'd really value your opinions :(
I was in a big Tesco Extra store on a Saturday afternoon, perusing the booze aisle
. Some teenage lad had been stocking the shelves with mixers, when his superior (I don't know he was an actual manager or just fulltime staff or what) - a rather big/well-built middle-aged man - came over. The lad said to his superior/manager he had managed to do x amount of the shelf, and the superior started having a go at him about not having done it, and started accusing him of lying about having done it when he clearly hadn't. The poor lad defended himself quite valiantly, repeating that he'd said he's done x-amount of it.
Anyway, things escalated til the superior was out and out shouting at this poor lad in the middle of the store . The teen at one point said "I can't believe you're talking to me like this on the shop floor" and the superior just kept shouting. In the end, the lad said (and I'm not sure there was anything else he could have done at this point) "my shift is over, we'll talk about this in the office when I come in tomorrow". Cue lots of "no we won't, we'll talk about this here, now!" At this point I honestly thought the superior was going to grab the lad and punch detain him - instead, the boy walked out of the aisle and went out the back (I assume) and after a moment of jaw clenching, the superior charged after. Goodness knows what happened after that, I but I'd assume at some point between 1pm Saturday and 10am Sunday, this boy lost his job.
Now I'm sure there will have been mitigating circumstances - people don't shout at people who are generally good workers (do they?) - but showing that level of agression on the shop floor is wholly unprofessional. I was very intimidated.
Thinking back I'd have loved to walk over to the superior/manager and tell that every employee in entitled to dignity in the workplace, and that he was being very, very unprofessional and, frankly, needed to get a grip. But he honestly looked like he was about to flip and I was afraid it would be directed at me (fwiw, I'm a twenty-something girl ).
Getting home, I wished I'd reported it to the store manager, but a) I didn't see his badge to take his name, and b) I was kind of worried I'd ask for the manager and he would walk out of the office iykwim 
Either way I'm heartily ashamed to say I just left the store, having watched a young man just take all this abuse :(
WIBU to have not gotten involved? What would you have done? I'm honestly kicking myself over it, and I feel really rotten that I could have intervened and didn't, as I'm sure this boy won't have been the first and won't be the last :(