I was in just such a situation the other day. All four cars were stopped. The car in the left turn lane next to me made a left turn. I checked the car coming from the right. He made no indication that he was going to proceed into the intersection, so I started to enter the intersection. At that time, he decided he was going to enter the intersection, so I stopped to allow him to go ahead. As he proceeded through the intersection, making a left turn in the process, he flipped me the bird. So, I gave him a thumb-up in response, and life went on.
Multitasking?