Well to me, the Maga evangelicals are not insincere. But they sincerely believe that to practice their faith they must control others' choices. I don't see abortion as much different from blue laws. YOU can't do something that doesn't affect me! OF course, the cries of "but the unborn souls." They may be sincere, but their sincerity only affects the souls they believe they care about, which is shown by their lack of commitment to poor children here or in gaza.
In short, it's about power of them over others. It's may not be sincere, but it doesn't have jack shit to do with christianity.