Yep, he was just being careful. You may have known your intentions but he sure as hell didn't. For all he knew you didn't see him and were about to pull in front of him. In Ohio (and I know you're not) a left turn lane, it is just that, a left turn lane, not a lane to use for your convenience until you can move to the right. Maybe a "Thanks, but I saw you coming" would have been better than a "what the hell".