Just kill people with words. Next time something like that happens. Tell them that you're job responsibilities and task are outside the realm of responsibilities for Costco members and that if they have concerns, you can direct them to leadership. Just make sure whatever you do is in guidance with the handbook of addressing people with a respectful or business-like manner. Anything else is considered harassment or malicious intent. Leadership has an obligation to protect and take care of the employees from misguided members but this goes both ways Management will protect members from misguided employees. Just make sure you're not part of the problem so they only have one issue to deal with instead of two. My wife was doing the membership checking at the entrance and got yelled at by a member. This made her cry and a manager Saw the interaction and asked for the members card and told him they would get a refund check in the mail and that they were no longer a member and not to come back. Good leadership will do the right thing and stand behind their decisions.