Fredo was such a pacifist, maybe he was left at the door by gypsies like his mother told him.
Who opened the drapes inside Michael's bedroom? Fredo? If it was Fredo, then how could he possibly think he was lied to?! That is to say, if he was instructed to open the drapes, what the hell did Fredo think he was doing that for?!
Someone probably told the housekeeper to stay out of the room, hence, curtains left open. Of course we never see a housekeeper, but folks with that kind of money always have a housekeeper, who is probably the one who closes the curtains when night falls.
