Following my previous post on things I learned at Bible college about how to have a reasonable discussion, here is another: you need to accept that people are inconsistent.
That is to say, it is entirely possible that someone you are debating with will hold two opinions that you believe cannot logically be held at the same time. In a reasonable discussion, you need to accept that this is so without assuming evil intent. One good reason for doing so is that it’s probably true of you also – no-one currently on earth has a worldview and set of opinions which is entirely self-consistent and logically perfect.
What you should not do is claim that one or both of the views “isn’t really their view”, or that they are lying or dissembling when they claim to hold both. You are, of course, entirely entitled to point out the inconsistency as you see it, and ask them how they reconcile the two positions. It may be that they haven’t noticed the conflict, and this will cause them to think. Or it may be that you haven’t understood their position fully, and after discussion, you agree the two views are actually compatible. Or it may be that your worldviews and base assumptions differ to such an extent that what you believe is logically impossible, they think is logically fine.
The clearest examples are also the most controversial, but to try and illustrate: some people I talk to cannot understand how my beliefs about church leadership are consistent with with my view that everyone is created in the image of God and therefore equally valuable and important. But I, of course, think these views are entirely consistent. And I often cannot understand how the views on human rights espoused by some people I talk to are consistent with with their views on abortion. But they, of course, see no conflict. Regardless, in either direction, it’s not OK for either me or them to make bold statements that the other party is a liar, is debating in bad faith, or is in other ways evil just because, in that party’s opinion, the other person’s set of views is not logically coherent.