Most people would move on. Just like most people would not stand up to a robber at a minimum wage job. But those who do make it a tiny bit less likely that you

Most people would move on. Just like most people would not stand up to a robber at a minimum wage job. But those who do make it a tiny bit less likely that you or I will face a similar situation. So it's not appropriate to call them stupid or question why they did it. You don't have to praise them, and you don't have to emulate them, and they may be stupid, but you should be silent - they are providing a tiny bit of deterrence to antisocial behavior everywhere.