Leaving aside any hard solipsists who are excluded by the humans existing idea, then the humanist and theist start in the same place.
That's registering a 10.5 on my 1 to 10 scale of wrongness.
I assume that for the theist the bottom line moral standard is his or her god, who is typically deemed to be the source of all good. The Good itself, let's say. On the other side, the humanist would presumably say that the weal and woe of humans is the
ne plus ultra, the gold standard of morality.
There may be overlap in many respects on specifics, but as foundational assumptions these things can't be reconciled.