It is very common for people to have a drink or two after closing when they work on the premises. It is usually OK'ed by someone in charge. Whether the person saying that it is OK has the authority to do that is another matter. At one festival (before it went live) I was doing night shift, it rained for the entire night. The person in charge of all security on the site was taking people one at a time to a tent where there was coffee facilities. I went and had a coffee when it was my turn. I wasn't told that the people who owned the tent and coffee had not authorised this. Technically it was theft, but I thought that if the supervisor was organising it, it was OK. Going back to the pubs and clubs, some allow a drink or two after closing as a perk of the job, it is sanctioned up whatever chain of command it needs. Others have a manager or senior barman that encourage it but the actual owners haven't sanctioned it. Often the staff aren't aware of that.
As for judging him. What I was getting at was that you shouldn't just write a person off because of a couple of incidents, especially not ones that far back and when they were young. It tells you a little bit about someone, but you have to be aware that it is only a little bit.