I think you are wrong. Christians here have meekly put up with abortion for 40+ years, I suspect they will not do much of anything about this either.
For Christians, this situation with homo marriage differs from abortion.
The pro-death crowd doesn't target Christians, whereas the pro-homo crowd does.
So it won't be a matter of "not doing much of anything" because Christians are facing an existential threat from the homos. Christians will react.