Some people just take a while to absorb new information.

My father would always seem like he was completely stuck in his ways and unyielding if you argued with him for one day. But if you came back the next day, he usually had a much better view and had accepted some of your statements.
I actually enjoyed debating him once I learned this, and learned to drag out the debates over several days. I also understood a lot more by copying his method of learning.

Not everything needs to be instant. Give people information, then give them time to think about it.