The point though is that Eru is beyond good/evil, he is at once both of them, and he creates the circumstances in which both enter the world. Eru just is. And why should that be a bad thing? I certainly haven't got a dislike of Eru, in fact this seems much more natural.
It's up to the people of Arda to discover what is right and wrong, and there are indeed things which are right and wrong, for them (but not equally for Eru), it is not a moral free-for-all. Likewise its up to the reader to discover these things too. They are not necessarily set down on the page for us - Gollum is an example of that. If there was a strictly laid out moral objectivity then Tolkien's work would have been incredibly didactic and that's one thing that it is not - or else why would be discussing this now?
This world is not corrupted by evil, it is created from the very beginning with evil inbuilt, into the very fabric of its being. There is no 'paradise' from which the Children can fall because the world was fallen before it even began. That's an essential and crucial difference between the way Tolkien's own religion saw the world and the way he created his own secondary world. It underlines the Long Defeat. But I reckon, Child, that you get around to that thought anyway! The problem is that if we apply Tolkien's own earthly religion to this idea of Eru being a whole law unto himself (which he clearly was, as Tolkien tells us that) then we start to get into torturous argument because it just doesn't 'fit' snugly. And thus, if we look at the Drowning of Numenor in the context of Eruism, it becomes less morally contentious.