When you meet people like this there are no 'tactics' ... it's just about presenting the truth in good faith as you see it and listening actively to understand their point of view.
The problem I encounter is that many people posture as 'open-minded', but in reality they want to hear your opinion for the same reason an opponent wants you to show your cards after they've folded to a successful poker bluff. In this case it simply tells them "what side you're on" or "which tribe you belong to".
As a heuristic, I've found it's very difficult to formulate thoughtful questions if you're not genuinely curious about a topic. Therefore, I tend to use the 'questioning level of thoughtfulness' (QLOT) of my discussion partner as the signal of whether or not I'm dealing with someone who desires a good faith discussion.