Keep going. Look at Matthew 7:6. "Do not give dogs what is holy, and do not throw your pearls before pigs, lest they trample them underfoot and turn to attack you."

That is (in this context), don't bother trying to give truth (or even have a reasonable conversation) with those who simply will not listen. Zealots, shill, propagandists... it's like talking to a brick wall. If anyone has a technique for getting them to stop being a brick wall and start actually engaging with what you're saying, I'd like to know what it is.