That varies from person to person, far too much to be entirely useful. I personally prefer the discomfort test. "How uncomfortable does this point of view make people, even if their whole culture does it." The Romans practiced infanticide yet they knew something was wrong with it. Americans practiced slavery but they knew something was wrong with it. In my experence, Americans have abortions but most know that there is something wrong with it. It isn't difficult to make people squirm, which is why the most common response to the abortion issue is, "I don't want to think about it."