To reply to the OP - you were absolutely in the right. One the things that angers me the most in the security line is people who stand around hesitant to go up and put their things in the tray.

If he was desperate to make sure that his tray hit the conveyor belt before yours (which it probably would have done anyway - you presumably weren't blocking his trays assuming he would get ready ahead of you) then he could have slid his trays down the ledge after the person infront of him departed - there's space for two so the full length of the loading area should be used!