They would be wrong about the first part, but correct about the second, at least partly.
Why not just have "civil unions" with the same rights and responsibilities as marriage? Just call it something else besides marriage. It would be so simple. Gays could have a wedding, call each other "my wife" and "my husband", they could have a "honeymoon", they could even use the term "marriage". It just wouldn't be called that officially. What is the big deal?
because its not justified.