Yet you are all missing the point!
Having an abortion:74%
Practicing polygamy: 86%
Mormonism is not really anti-abortion, although they do want control over Mormons having abortion, that is why Bishop and Cardinal Mitt Romney could be so passionately and publicly pro-abortion, and still be among the holiest and devout Mormons, like Harry Reid.
It’s not immoral for the 14% who have several wives.
So why is polygamy more ingrained within Mormons to be something against than even abortion?
'Tis a complex response...and no one thing addresses it all.
But some clues exist:
(1) You can be ex-communicated for being a polygamist this side of the grave; whereas with an abortion, why, you might even have the Mormon gods giving you the prayer green-light for one! So...there's a pretty good internal motivation for establishing your standards.
(2) Externally, Mormons know that their reputation has been more formed by their polygamous 19th century and first half of the 20th century...
...than, say, their doctrine of pre-mortalism whereby supposedly other-worldly spirits await pregnancies to come down & inhabit bodies...
...hence, they are more likely to "straight-arm" polygamy as a defense of "Well, that's not who we are...anymore..." (as if their church doesn't still teach eternal polygamy for both past polygamists and those who marry more than one wife eternally in their temples)
(3) Finally, Mormonism is more of a dictatorial legalistic religion...with their general authorities & personal bishops operating as mini-dictators. So, Mormon statements have been made saying they have NOT addressed -- either pro or con -- any pro-life legislative proposals...
And, frequently, abortion is sub-sumed by many other issues. One man, one wife, HAS, however, been supported by the Mormon Church (California Proposition that passed, for example)...
So, whereas the Mormon Church hasn't been 100% paper tigers on one-man, one-woman marriage, it HAS been with abortion. Obviously, their members DO tend to notice that, ya know.
Of course, other aspects are at play in all of this...so I don't pretend this covers all Mormons...but I think it plays a part with some -- even sub-consciously