Most democracies seek input from scientists to inform policies. This can put scientists in a position of intense scrutiny. Here we focus on situations in which scientific evidence conflicts with people's worldviews, preferences, or vested interests. These conflicts frequently play out through systematic dissemination of disinformation or the spreading of conspiracy theories, which may undermine the public's trust in the work of scientists, muddy the waters of what constitutes truth, and may prevent policy from being informed by the best available evidence. However, there are also instances in which public opposition arises from legitimate value judgments and lived experiences. In this article, we analyze the differences between politically-motivated science denial on the one hand, and justifiable public opposition on the other. We conclude with a set of recommendations on tackling misinformation and understanding the public's lived experiences to preserve legitimate democratic debate of policy.