John is almost disheartened by the fact that Dave is trying to leave, he watches him go for the handle, watches him put a foot outside of the car. After that John isn't thinking. John really isn't thinking as he gets out of the car faster than Dave and sprints to Dave's side.

John isn't thinking when he pins Dave against the door. John isn't thinking at all right now, he just didn't want Dave to leave so fucking soon. John has his hands on either side of Dave now, effectively pinning him to the car's passenger door. John is staring directly into what would be Dave's eyes if he didn't have his aviators on. John is determined to not let Dave leave until he gets his answer.

So John doesn't think and does something completely irrational. He saw it in a movie once he thinks. He's leaned forward, and he's kissing Dave. Not sure why he's doing it, but he's doing it. He supposes this really isn't Dave's form of make up though.