If you haven't realized it by now, there are victims covered under Jesus' "least of these" focus of Matt 25 that are entirely politicized in today's environment. You can't even talk about abortion w/out it coming under the political umbrella.
Therefore, somebody could always maintain that loving our pre-born neighbors as ourselves in the public square is a political activity and also a lobbying activity; hence, these folks conclude, we're not called to do that as our primary focus.
I'm not maintaining that a Christian will never venture into politics. What I am maintaining is that there is no law that will win the culture war. A ban on abortion, while a good thing, will not win the culture war. What will is bringing people to Christ so that, hopefully, they wouldn't even consider such a thing.