At his blog, Thomist philosopher Edward Feser quotes Michael Levin as saying: “What homosexual rights activists really want [from anti-discrimination laws] is not [merely] access to jobs but legitimation of their homosexuality.”
This is a distraction. The motive of activists is not what should be at issue, but what is right and true.
Perhaps Thomists should reevaluate the premises underlying their current opposition to homosexuality. Maybe the reasoning supporting the traditional view is wrong. And scientists increasingly inform these discussions, and need to be consulted.
Feser thinks the approval of gay marriage would require a revolution within Thomistic thought. But maybe that revolution is overdue.
In any case, the issue is far too serious to make it a face-off between liberal and conservative. Creative intellectual work needs to be done on whether a Thomistic case for same sex marriage is feasible and defensible.