Speaking from experience, most of us just don't want others' opinions shoved in our faces.
Ex. on the subject of gay marriage - it's only a few short steps from "Ok, gays can marry" to "I don't care what your beliefs are, Pastor - if you don't marry us we're suing you for discrimination." (See also: Canada, UK, that one florist)
Honestly, both sides need to stop in the middle - sure, gays can marry, but everybody gets a conscience exemption on anything that directly interacts with said marriage. If the pendulum swings all the way over, it's not so much "adding freedoms" as it is "exchanging one group's freedoms for another's." Which is what a lot of Christians see happening, hence the opposition.