(Christian here) To be fair, Mary didn't cheat on Joseph with the Holy Spirit.

She was raped by him.

I don't say that lightly, but if she had cheated with her heart on Joseph, then he couldn't be asked to stick around. It was an unwilling/unknowing act on her part (so the story goes) and as such Joseph was counseled appropriately.

And Fact #2 is the funniest thing I've read all week!