Genocide deniers who refuse to look at testimonials ("WMD! Incubator babies! I don't trust Western media" etc) aren't actually deniers at all. If someone is refusing to read up, it's because even one refugee account would shatter their worldview, and that terrifies them.

Readjusting your politics to fit the facts in front of you is hard work. It requires enough confidence to admit that you were wrong and that old frameworks no longer work. It can be emotional to have to abandon a belief you may have invested years or decades into.

But in the end, that's the only real option. Ideological fragility is not an excuse for denying the suffering of others. Plus, if you dig in your heels long enough, you'll just end up living in a fantasy world.