Katy Zane. Wrong. The fact of the matter is, seeking legalization of things like abortion and same sex marriage is not against Mormon doctrine. It does not make one an unworthy Mormon.

It is against Mormon doctrine to participate in such things, for example, for a Mormon man to marry another man. Or for another example, it is against Mormon doctrine for a Mormon woman to go and get an abortion (unless it is from rape or incest).

NOTHING. Absolutely NOTHING in Mormon doctrine says that we are commanded or that we must stop others from doing these things. Mormon doctrine does not say to stop the atheist man from marrying another man. NOTHING in Mormon doctrine says to make it impossible for the Muslim woman to get an abortion. So on and so forth.

So no, supporting the legalization of these things in no way runs counters to ones own faithfulness to Mormonism. If it was the case, every single Mormon politician better be trying to outlaw tea and coffee, and to ban the eating of fruits out of their season. Seeing how the Word of Wisdom is just as much a factor of being worthy than anything else in the Church.