Continue to talk to him, continue to engage whenever it's possible for you. That goes for anyone you believe to be genuinely misinformed.
Due to a myriad of factors, not everyone has the same level of understanding or reasoning, not everyone is on the same page. Some people have been exposed to misinformation for so long it shapes their overall worldview, which makes it rather difficult to convince them otherwise.
If we want ignorant people to stop being ignorant and start expressing themselves more in line with truth and reality. Shouldn't we take up the responsibility to engage them and inform them, whenever it's within our means to do so?
If you're willing to complain about people falling victim to falsehood, then set them on the right path. Give them counter-arguments with proper sources, so they are better informed and are able to make the conclusion more in line with the truth.
As an individual, that's the most you can do. You can't force them what to believe, but you can meet them halfway.
That is if you care enough about that person, to begin with.