> I realize a large portion of the rest of the world sees it differently, but I'd place it in the same category of a CEO donating money to the KKK or other extremist groups

At the very least, that depends on whether you take his position as being an extremist "anti-gay" one, or simply as upholding the then-current status of traditional, cross-sex marriage. It should be noted that same-sex marriage has not been introduced by overt policy in the U.S.; it has acquired its status via a judicially-introduced "extension" of the usual cross-sex marriage. This surprising development has contributed to its wide-ranging acceptance in a way that shouldn't be misunderestimated; far from being something "contrary" to existing tradition, same-sex marriage has simply joined a lengthy list of comparable legal fictions known from the history of Western jurisprudence.