Only? Sorry, Evangelical Christians have been on the front line more than Catholics.
Fundamentalist Christians have never wavered in our opposition to it, not an iota, but I can’t say we’ve been on the front lines, as most fundamentalists don’t see the point, after a certain point (voting, mainly) to get involved politically. The few fundamentalists who have gotten involved politically (Jerry Falwell being the most famous example) have almost always wound up moving into the evangelical camp. Fundamentalists are more about remaining separate from sin, but the battle lines are being drawn now to where we will be forced to make a public stand (not that our stance isn’t already well-known, we just don’t get in the news about it). The clueless media doesn’t know the difference between “evangelical” and “fundamentalist”.