[GunRunner]

For the same reason loving God is loving.

There's not really any evidence for that. If there is a Creator, the evidence points to indifference, not love. The rain falls on the just and the unjust alike.

[reasonisfaith]

You asked why is loving God moral.

Here’s another form of the same answer:

The same way your existence is equivalent to being.

[Olog-hai]

That reference to Matthew 5:45 sounds like an act of love rather than indifference, which would indicate withholding rain from all whether just or unjust.