Sounds a lot like my brother. He used to email me with propaganda from his political and anti-science ideology. I would respond with facts and evidence. Then he would resort to ad hominem attacks like "Well, you're just stupid." Eventually, he stopped sending the propaganda, though he still seems to believe it.

Some people will go to any lengths not to be contradicted. However, I still point out to people what the facts are, and point out some source information. Why? Because I look back on phases in my life when I accepted fallacies as if they were true. When people tried to correct me, I rebuffed them in the moment. However, the truth they offered stirred within me, and I would eventually come to realize that those who tried to correct me were right. Unfortunately, by the time I came to the truth, many of my helpers had moved on, and I could not locate them to send my thanks. Therefore, I can only hope that the seeds of truth I offer people will eventually grow within them. Even if I don't see their fruits come to maturity, I maintain hope that it will happen.