As labels go, "Interfaith" is broad, encompassing everyone from mostly secular, even atheist couples who come from different backgrounds, to deeply religious couples who are committed to different faiths. The "interfaith" label may be the only thing these couples have in common. I choose symbols very carefully, making sure that no one has to choose something that doesn't fit or that makes claims on their identity that they are not ready to embrace.
It seems self-evident that everyone deserves equal rights on a governmental level. I don't need to rehash arguments better stated elsewhere. On a business level, it also seems self-evident that customers deserve good service. But neither of these are the real reason I have always made a point of having same-sex ketubah texts (since 1999 when I put up my first ketubah website). The real reason is that I like having Gays and Lesbians around.