As a guest at a friend’s gay wedding, Peter Stanford (26 July) had no answer to an “elderly man” at his table who accused the Catholic Church of homophobia because, in opposing marriage redefinition, it favoured treating gay people differently from straight people. He wondered if any readers had an answer.First, it is not discrimination for the law to treat different groups differently for a good reason. Even after redefining it, UK marriage law still excludes various groups in order to protect the meaning of marriage: minors because marriage requires freely choosing adult responsibilities; those already married because marriage requires sexual fidelity; or multiple unions because marriage is between two people. The law has always excluded same-sex couples on the same gr