Give them Space

You're about to make a very important point.  You're sure you're right.  You're expecting some opposition.  Use my third principle to get a fair hearing.  It's the principle of the Tentative Statement.

Before I explain, I want to make clear that I am not asking you to ignore facts or compromise principles.  I am suggesting that you avoid statements that will allow for no retreat. Use phrases like "because of x I think y."  Your listeners can then bring other facts to your attention, or offer another interpretation of your facts.  This will avoid some of the raised voices and flat contradictions you might otherwise encounter.

You've worded things in such a way that you are not making pronouncements from on high.  You've created a dialog.  If someone doesn't like something you say they are bound to talk about it.  They may as well say their piece directly to you.