I know nothing about your situation with the guys at your retail location, or the seriousness of it, or your specific store culture. Instead, I can share a story that I was told by a manager at a retail grocery.
The produce fellows were working with stacking the fruit and vegetables, but would always stand facing the bakery, for some reason. The manager finally figured it out. There was an attractive, curvy woman who worked in the bakery. The manager spoke to them (produce) directly to stop staring at this employee and any employee in general. He did it because although the woman seemed to actually encourage the attention, it was a problem for any retail manager and needed to be addressed right away. In that manager's opinion, this is sort of routine type of employee feedback, (along with showing up on time, doing the job correctly, not hiding from customers, etc) is part of his normal daily job and the reason he is hired to be a manager. The earlier he addresses small issues, the better.
The produce clerks -- well, they were bored, and did not have direct supervision / feedback until the manager said something and the work was not that interesting but the woman was. It only took one comment to be fixed immediately.
Extrapolating to your situation, I hope that this is just a direct cause of night shift casualness and a lack of management / supervision during the shift, not a cultural thing at the store. The manager I talked to would have much preferred to know about this early, to address it before it becomes a *problem*. OTHOH, I know a few stories from the 1980's with actions we would consider quite serious today (not direct assault, but more related to jokes, stares and drinking in the store after shift ends in the evening. The culture follows the manager from store to store, so he is the best one to address an issue).
A second story for fun:
-- I was on the team that did time and motion studies to determine how many hours a store needed to operate, especially stocking and front end customer service. We had to collect data 24 hours from the stores, and make randomized mini observations on everyone for 2 weeks. The night shift observers reported a problem to me -- they could not find the janitorial crew for hours at a time. They just disappeared but were still in the store. It turns out that the janitors were arriving a bit early, working hard, sleeping in the washroom for 3 hours and then finishing up just before the next day's team lead would be walking through. (e.g., not getting the extra work done, just the basics). Because of the confidentiality to not name persons with the study, we could not tell management anything specific, other than reporting that the observed janitorial shift at store X is from 10pm to midnight and 4am to 5am. I hope they figured it out.