I don't think the parent referenced Republicans or Democrats at all. The parent was talking about "conservatives". And anyone who opposed same-sex marriage in 2004 -- Obama included -- should absolutely be counted as having (at least some) socially-conservative views.

Obviously many people changed their minds since then. It is perhaps notable, though, to consider that most of the people who changed their minds since then identify as Democrat, while many more Republicans continue to hold such backward, discriminatory views.