Reactionary

A reactionary is someone who wants to restore an older, less socially advanced, regressive social order in reaction to the contemporary social status quo. In contrast, a conservative is someone who merely wants to conserve the current social order against more socially progressive challenges.

Someone who wants to increase restrictions on abortion thus is a reactionary whereas someone who, for instance, opposes gay marriage (outside of those places where it is legal) is a conservative.

The opposite of a reactionary is a progressive.