Etiquette question: sitting out after your button

[sweetjazz]

Please tell me if you consider the following actions okay or douchey. (FWIW, I am thinking of these situations from the context of a medium stakes player, so there are always other games available and plenty of fish in the sea.)

a) You are sitting at an FTP HU table with autopost blinds on. A player you recognize who you don't want to play sits down and the hand is dealt. You play your hand, sit out and leave.

b) You are sitting at an FTP HU table with autopost blinds on. You do not recognize the player as you begin your match. During your second hand, PokerAce loads the stats you have on this player. It turns you have datamined a lot of hands on this player and from a quick glance at his stats, you can tell he is a clear winner and you decide you do not want to play him. After the third hand (your second button), you sit out and leave.

c) You are sitting at an FTP HU table with autopost blinds on. You begin to play a match with another player. About 70 hands into the match, you realize that you are planning to meet a friend in a few minutes. In the hand you are currently playing, you are the big blind. You decide to play one more hand (with the button), and then sit out and leave.