Apparently one of the supporters is the Center for Reclaiming America for Christ. According to the Montana News Association, the organization has alerted its 800,000 membership to boycott the automaker and its products. The Center plans to present a petition before Ford's shareholders meeting on May 11th.
More details and the petition can be found on the Center's website. Note that Ford has recently had its request not to submit its stance on gay rights to its shareholders for a vote by the SEC.
[Source: Montana News Association]