If you are Evangelical and Pro-Life, you subscribe to two sets of beliefs that strictly curtail the behaviors of other people.
Beliefs alone do not curtail behavior; hence your next sentence mentions enforcement. To repeat my example, I may believe eating meat is unethical. This alone would not curtail anyone's behavior. I might advocate for some kind of enforcement, or I might try to peacefully persuade people that my position is correct, or I might quietly fret and wish the world were a better place.
It seems to me that you are assuming that people who oppose these behaviors must necessarily approve of exercising government power to dissuade or prevent people from the behaviors.
It is hard to have a discussion when you get to define the terms. Don't some pro-life people condone abortion when the life of the mother is in jeopardy?
I think I understand your big idea, and I don't discount your concerns about a slippery slope. I just find your language very absolute and self-righteous, the same characteristics that make it hard to discuss ideas with a religious ideologue. ("You cannot be evangelical and pro-life and support limited government" -- when, again, enforcement of morals would be a very small slice of government activity, and doesn't everyone support a limited government to some extent?)