An answer that's likely to displease both sides of the issue...
The root problem is the unequal treatment of the genders. Of course, you say, that's sort of obvious, isn't it!
Yes, there are aspects that are obvious on the surface, but I don't think we understand how deep it goes.
From the beginning of history, people have taken advantage of each other. The strong and dominant rise to the top. If it's at the expense of the weak and vulnerable, that's always been considered par for the course. We have always tended to think of those at the top as superior to those at the bottom. Kings are superior to the gentry, who are superior to the peasants; Masters are superior to the slaves; the rich are superior to the poor, bosses are superior to their employees - and yes, men as superior to women. That's on the surface.
If we look at what actually happens, we get a different picture. Often, we see the strong standing on the shoulders of the weak (in which case, who's actually stronger?). In ancient times, it wasn't uncommon for an illiterate slave owner to have a well educated slave whom they set to work tutoring their children, or other tasks requiring up to date know-how. Aesop, famous for his fables, was a slave. To this day, we often see bosses and team leaders who are less skilled in key areas than their employees.
In too many cases, we see people who were good at their job elevated to the position of a boss, and find they make a bad boss. They were better at what they were doing before, because that was their skill set. The previous boss was actually good at being a boss, though he didn't have the skill of the first person. Now, he’s also been promoted beyond his level of ability.
Different skill sets, yes, but who's superior? Who is higher on the social ladder? Who gets use of the executive lounge? Why?
And how do you explain to your neighbours, or to your mother-in-law that you turned down a promotion because you've already got the job you're good at - without sounding like you're making an excuse?”
I think it has a lot to do with having eaten of the fruit of knowledge of good and evil.
Now, if we look at the world of women, we can also find a lot more below the surface. Throughout our male dominated history, we do find a few outstanding exceptions to the all too pervasive meek and dependent role of the female. In the Bible, we have Moses’ sister, Miriam, and the four daughters of Zelophehad. And what about the prophetess Deborah? Even the Apostle Paul, who on the surface seems to favour a male leadership in the Church, yet highly praises such female leaders as Priscilla, Junia and Phoebe. In his instructions to Timothy and the Corinthians, Paul was only dealing with facts on the ground; women who are illiterate, and have hardly ever been outside their home (like most women of his time), don't make good leaders. Paul was simply being pragmatic, not speaking ex-cathedra.
In secular history, there's Cleopatra, Nefertiti, Joan of Arc, Elizabeth the First, Victoria… And look at recent history: some of the most male dominated societies in the world, like Pakistan, India, Bangladesh, Turkey, have had female prime ministers, while the “most modern country in the world” hasn't had a single female president”. The two female prime ministers UK has had were anything but the “slap-your-face-with-my-bra” types.
Often, the very fabric of society, even the most male dominated, has been held together by the women, the mothers. They handle the family finances, keep the family in line. The men have the positions, the power, the salaries; but they spend their money before they get home, leaving their wives to come up with the extra money to feed the kids, keep them in school, and keep the world from falling apart.
So who's really superior? How are we equal, or unequal? Does equality mean uniformity?
Can we be free to take a good look at the strengths and weakness of either gender (or of any other classification, for that matter) without offending the social justice warriors?
Fathers are different from mothers. At their best, each adds a different aspect to the stability and quality of a family. Women bosses add something to a company or a team that men bosses don't, and vice versa. The same with women heads of state.
That's in a perfect world. The world at its worst?
Women are more responsible than men. Why? Women get pregnant, and are stuck with the kids, while the men are free to run off anywhere they please and make more babies. That's the very factor that has always made women weak and vulnerable, and it's also the source of their strength.
So, how do we equalise things? Do we try to enforce uniformity where it doesn't exist? Do we say to the women, “You don't have to go through with this pregnancy”? That will only make women just as irresponsible as men. Equalising by dumbing down is not the answer.
What if we didn't choose the easy way out? What if we put the same expectations on men as we do women, and make them just as responsible for a pregnancy as the woman? What if a woman's maternity leave were at the expense of the child's father? We now have the technology to prove who the father is.
This would have to go far beyond the legal issues. It requires a cultural change. What if it were just as much an insult to call someone a “playboy” as a “slut”? What about adding a few mandatory titles to men's names to alternate with “mister”, the same as women have Mrs, Miss, and Ms? What if a man's reputation were just as tarnished by how many children he's fathered (by as many women), as a woman's is by how many times you see her pregnant?
Can we hope for a society like that?
Okay, my opinion on abortion: I believe it's wrong. I believe it's murder. By allowing it, we're taking the easy way out, enforcing equality by forcing uniformity where it doesn't exist.
On the other hand, by campaigning to make abortion illegal, without giving equal attention to the other issues I've described above, we Christians become nothing more than a bunch of hypocrites. Had we been fulfilling our mandate all along - the mandate that was pushed forward by the likes of Hannah
Moore, William Wilberforce, and others, that gave birth to the the women's suffrage movement, the abolition of slavery, child labour laws and other reforms - we could have led the way towards equality of the genders, thereby preempting the excuse of legalised abortion as an equaliser.
On the other hand, if we now deprive people of the legal avenue of abortion, while keeping them from state aid to enable them to support the children we're trying to save, we place ourselves as the target of Jesus’ condemnation: “They tie up heavy burdens, hard to bear, and lay them on people's shoulders, but they themselves are not willing to move them with their finger.” (Matthew 23:4)