No one really has an argument against it other than that they don't personally like it, and the expectation that for some reason everyone should agree with the morality your culture happened to impose on you.
Further, moral relativism is a dangerous and absurd position to hold. It might be convenient in excusing something you hold that's controversial but it also means a group of people can use it to defend any position at all they have. Any familiarity with what we humans have done and do should tell you this won't be about excusing disagreements over irrelevant things like ice-cream flavors.
https://newlinesmag.com/essays/oxford-study-sheds-light-on-m...
Mohammed got his start by marrying a wealthy woman, then he started businesses using that wealth, then he could relax, create a religion and marry many women including children. He co-opted already existing single deity systems and brought that to the Arabic world. He copied a business idea basically.
How is this guy any sort of role model?