I have reasons for not wanting to include them. They might not be 'good' reasons, but they are still reasons.
This is not a valid argument in a liberal democracy, imo. It reminds me of the racist white Southerners (and white South Africans) who would say, "If you lived here you would know what we are talking about." Having reasons is not an argument.
Plain and simple, there is no valid reason for prohibiting marriage for gay and lesbian couples. It will not damage heterosexual marriage in any way. I wish for once someone would tell me how allowing gays to get married will do anything to my or anybody else's hetero marriage. If anything, it will strengthen hetero marriages, because fewer gays and lesbians will make the mistake of marrying straight in order to find acceptance in society.