I wouldn’t jump on to blame on the customer. In fact, have my own hill I’m fighting right now where I’m not completely in the right. Who knows, maybe the working hours were not visible, or maybe there was no closed sign at all. In any case, this made at least one person mad and is a perfect opportunity for a business to do a retro and check if they might need to do something about it. It’s much more valuable than a thousandth review from someone who had a great time… or didn’t, but didn’t care to review either. And, unless your business is genuinely bad, even a Karen once in a while shouldn’t affect the total score a bit.