If I understand your scenario correctly, there were two lanes going in your direction: one left turn lane, and one other lane from which people can either go straight or turn right. Correct? If so, and you were not positioned on the very far left of the straight/right-turn lane where anyone wishing to turn right could still come up and do so, then you were indeed being a jackass. How could you not know that someone may want to turn right and then maximize your positioning to allow them to do so?

I do it on my bike and I do it in my car. It's common courtesy! If the lane is too narrow for two cars to fit and therefore the second car would just have to wait, then so be it. But it is never too narrow to fit with me on my bicycle or motorcycle so of course I would position myself where it will allow someone to turn if they want to.

Your positioning is what made cars impatient with you. They wouldn't have been impatient waiting behind, say, a big truck at that light because they would look at the situation and realize that there isn't anything the truck could do to make the situation any better. It's the same reason people don't get mad at delivery vehicles, someone parallel parking, etc. But they look at you and go, "if that jackass would just move over a little...i could get on my way," and get impatient and since you didn't give them room to go by you on the right, they went by on the left. In other words, there was something you could do to improve the situation but you chose not to. That frustrates people. Don't be like that.