Baloney. It's "apples and weddings". This farmer has discriminated against no one at the farmers' market. The wedding venue is effectively a separate business (22 miles away) that has nothing to do with selling his fruit and vegetables at the market.
If you want to shut down his business of hosting weddings, fine, do that. But as long as he has no issue selling to LGBT customers at the market, then refusing to allow him to do business there is pure discrimination against HIM for his beliefs.