U.S. President Joe Biden defended workers' rights to form unions and warned against intimidation of workers in a video posted on Twitter on Sunday night, as Amazon.com Inc employees in Alabama vote on whether to unionise. Mr. Biden didn't mention Amazon, but specifically referenced “workers in Alabama” in the video and a tweet introducing it. He said every worker should have a free and fair choice to join a union, and no employer could take that away. “It's your right... So make your voice heard,” he said.