Why Do People Disagree About Good and Bad?

Even if you're religious, you still believe that only your religion is a correct one and all the other ones are basically wrong. We also have to account for how so many people can be wrong. Even within your own family, there's a lot of disagreement between you and your parents about such questions of good and bad. Nobody, almost no two people agree on what is good and what is bad. Just because you're certain of something doesn't mean it's true.