Well, we know thanks to Claire and Kate that what Michael said about the Others isn't true, even Kate flinched when he said they were like animals, going barefoot and wearing dirty clothes. She knew those costumes were only props.

Either Michael is really a fool or he lies.

I still think that the island is nothing but a fantasy, so killing Ana might have been a way to free her indeed.

I don't think that Michael planned anything concerning Ana. How could have he known in advance that she would have stolen Sawyer's gun?

I am not sure that Michael is completely aware of what is going on, but he thinks he knows something. The old Michael was a nice guy, he wouldn't have killed people just "to get rid of them" as if they were pawns, and because of some plan. He must know something new that justifies his actions.

And his current actions fit in what the Others have done until now.