Well, there can be non-religious people who oppose abortion. I know some of them. The difference is that they usually don't impose that opinion on others. They don't try to get abortion outlawed, and they certainly don't take guns to abortion clinics and shoot doctors, or intimidate young unwed pregnant women with picket lines. This is all solely the work of religious Christians.
There are atheist pro-life
activists who for the most part
do impose their opinion on others, and even attempt to get abortion outlawed. They are at an advantage in that they tend to use their
atheism platform to also speak out against violence, which may gain them a certain amount of respect to where they may not be accused of imposing. But I'm not all that sure of that either. And I don't think they actively oppose abortion with the idea of it just being an opinion mounted against laws they don't care whether or not are changed.
We also have peaceful demonstrators nearby to where I live that picket a local abortion clinic from time to time. While some, most, or even all may be Christians; some, most, or even all could be atheists. On the rare occasions I see them, I haven't identified their religious affiliation, or lack thereof.
The problem with the Christian/religion thing in the U.S., is that it's tough to distinguish
Christianity as a chosen way of life, versus
cultural Christianity. We can distinguish between Los Angeles Dodger fans (fanatics) who are non violent, from the small minority that are. But with Christians, it seems to be a lot
tougher. One of the ways we can know that there's a distinction, is that there are converts to
Christianity among
Christians. Basically,
Christians converting to
Christianity. How can that be? Basically, cultural Christians converting to choosing Christianity as a way of life.
One of the prime examples of this would be conversions within the prison system. One of the claims I've heard made by an atheist (who probably gathered the information from other atheists), is that the prison system is filled with people of religion; whereas there are fewer atheists in prison. Thus making the claim that atheists are more peaceful, less apt to commit crimes than those who have an apparent religious affiliation. What ever statistic was made probably merely identified those with religious backgrounds (church membership, traditional family denomination, etc.) as being those of religion. The problem here is that if, say, there are so many Christians in prison, why the need for Christian ministries that are there to introduce Jesus Christ in a personal relationship context versus merely holding services for those that are already Christians? And of course, why are there a significant number of converts, many of them probably those counted among those already associated with Christianity?
If we can begin to make those types of distinctions, then it may be easier to identify existing cultural Christian traditionalists who view things like atheism, abortion, etc., akin to anti-Americanism, Communism, etc. And better distinguish them from Christians who oppose abortion, but also shun violence.
Sorry for choosing the road that may be going off topic, but I honestly don't know a lot about the other
Muslim issue you brought up.