I get what you're saying but that driver behind you did not almost crash into you because you decided to abruptly slow down. He almost crashed into you because he did not maintain a safe following distance, wasn't paying attention, etc.

It's insane how normalized terrible driving is. I don't even mean following the law at this point. It's much more basic than that and applies to every vehicle in every context. You must drive in such a way to be able to stop in time if the vehicle in front of you decides to apply max braking. This is dictated by the laws of the universe we exist in, not by some rule arbitrarily decided by humans.