But there are many which present a 'grey area' and one cannot assume they're self-evident truths. For example, the issues of abortion, carrying guns, marital infidelity, religious practices are all open to widely opposing views.

The fact that some matters are "open to widely-opposing views" doesn't mean that all of those views are legitimate. If you oppose abortion, well done you. You are misguided but I can see your point of view. If you propose that women should be prevented or restricted from having abortions, you are disgusting. Why? Because, by your own argument, there are opposing views. But a view is a view, not a cast-in-stone truth. So you have no right to insist that women should all have to adhere to a policy dictated by what is simply your view. That is what the anti-abortion movement wishes to achieve and that is why it is a baleful and wicked movement. It does not acknowledge in the slightest that any other view could be valid. You do have the right the make the case against abortion, weak though it is, but that's where it ends. You have the right to practise whatever religious delusion you like, and I'll defend that right to the hilt. But your religious belief is one point of view, not a truth cast in stone. So you have no right to foist that view on anyone else, or tell people that you are the possessor of the one and only truth. Unfortunately, the sine qua non of organised religions is to foist their beliefs on to as many people as they can, including babies. Such people are not executing their point of view as a point of view, are they? They don't recognise, by so doing, that other views are legitimate. If you want to argue that people should be allowed to carry guns willy-nilly, you are arguing that people should be allowed to go around always prepared to kill other people summarily. I can't think why else a gun should be carried in the pocket. That flies in the face of everything we're supposed to espouse about justice. Yes there are lines that can be crossed, etc., but I will never accept that those lines are infinitely elastic so as to allow disgusting opinions to be expressed without firm rebuttal and ridicule.