Here is the statement from the East Lansing Farmer's market:  Note that the requirement is for both the Farmer's Market and GENERAL BUSINESS PRACTICE.  He knew the rules.  

“The Country Mill has been excluded from the East Lansing Farmer’s Market because the East Lansing Farmer’s Market policy requires that all vendors comply with the City’s Civil Rights ordinances while at
the market and as a general business practice. Contrary to this policy and the constitutionally protected rights of all couples, The Country Mill has advertised that their business practice is to prohibit same-sex
couples from holding weddings at their orchard in Charlotte, MI. Their business practices violate the City of East Lansing’s long-standing ordinance that protects sexual orientation as well as the Supreme
Court’s ruling that grants the right for same-sex couples to be married.”