The advocates of same-sex marriage also point to self-selected and snowball surveys (from, say, popular magazines) to make this cases. I've seen academicians -- who should know better -- point to this notoriously unreliable survey data to make favorable comments regarding homosexual marriage / families / coupling, etc. Compare with the study data from Mark Regnerus and more recently by Paul Sullins. The latter is described here:
http://www.thepublicdiscourse.com/2015/02/14417/ Google on Mark Rgnerus Paul Sullins National Health Interview Survey British Journal Education Society Behavior Science.