Why do people think "morality" should play a part in government and politics?

First of all why would you ask if morality was just another word for opinion if you were going to answer it anyway. I'm going to ignore the fact that you did that and tell you that it is not "just another word for opinion." If I were you I would just delete this question because it is in no way making you sound intelligent. But I mean going along with what you said...morality should totally not play a part in government and politics. We should totally just legalize murder because in my opinion, it's totally okay.