You are either a Theist or a Nihilist. There really IS no other approach that makes a lick of sense.
For example, a person can say, “I think it is wrong to brutally murder someone.”
OK, fine, but why?
Maybe you don’t like it or approve of it, but WRONG? Just how do you know.
Because if there is no God, ALL is mere opinion–just an expression of preference and a will-to-power! There simply IS no morality of any kind if there is no God. There IS no existence as moral entities, any more than a hammer exists as a moral entity (a HUGE problem for biological reductionism, but that is a discussion for another day).
There is no more morality than saying that blue is “better” than orange. That’s all there is–a metaphorical stomping of one’s foot and saying, “It just IS!”
The best there can be is social niceties. But even then, the meaning of “nice” is personally and idiosyncratically derived! I say, “tomayto” and you say, “tomahto” and all that.
And Deism just can’t cover that theoretical/philosophical/logical ground. ONLY Theism can!
So one is either a Theist and can incorporate morality into one’s thinking, or one is a Nihilist and ALL is preference and a will-to-power. There simply IS no logical middle ground!