Actually, the Doctor did give Solomon 'a choice'. Something like "Leave this spaceship while you still can".

Yes, I remember that.

I also think he would have been willing to spare Solomon's life right up until Solomon kidnapped and threatened to "break" Nerfertiti. Which, if you stretch it sufficiently, could also be a sort of dark and twisted mirror, something to do with young women being snatched away.

Although if the Doctor actually sees it like that, I'd start to be very frightened of who he thinks he is right now.