Best way to communicate with a difficult supervisor?

One of my supervisors at work has a short temper, gets angry easily and expects perfection on every endeavor. If he is supervising work, he may stand quietly behind someone. If he is pleased, he says nothing, if not, woe to the person in question. He is this way only with certain people, me namely and it has been that way a long time. With me, he is very smart-mouthed with the very least encouragement. He's very cordial and kind and helpful to many others. I have no idea what I did wrong, or didn't do. Its been mentioned by him that I should consider management. About two months ago, our level of contact tapered off at his doing. I have been going along with it. However, I had a pword for one of our systems that only he or another person in his position can change. No one else was available so I went to him. He seemed okay with processing this for me. He made a little joke that I can barely remember but laughed a little. I just needed my pword changed. When I asked could he change it, he said he could. When I asked would he change it, he said he would. Before he changed it, he asked why didn't I remember mine. I told him that it had been a long time since I used it. I was told that that was no excuse. People forget things, I'm human just like any other person and don't understand his reasoning, especially when its not a system that is used on a daily basis. I like things to run smoothly, what would you suggest, besides staying away from this person who I really can't completely avoid? I also would like to delete this manager off my facebook page but wonder whether or not this is a smart move? I would be even more comfortable if he would simply delete me. Please help.