Yes, but you had a good ride anyway. Don't let them get to you. Four times is alot but I regularly encounter people like this. I think it would be hard to show with icons the message you want to give. Bike between cars might look like splitting lanes, your avatar might be biker in bike lane or shoulder, hard to tell. Maybe some one else can think of a way to show what you are meaning to convey.

By riding in the middle of the lane you are telling motorists that you have a right to the road. They get the message but they don't like it. Be safe, don't get too confrontational, they do want to run you over but usually won't do it because they know there will be some paper work if they do.