More generally, to what extent have people's beliefs about the possible political consequences about specific outcomes affected the science in ways that are not epistemically justified? For instance, do people who are more risk-averse tend to exaggerate the harms, so that they can convince a less risk-averse public to take action?

That seems likely, given what we know of human biases, though I think that people would normally do that unconsciously rather than intentionally . This paper by Alhakami and Slovic shows that people who think, e.g. that nuclear power is risky don't think it's beneficial, while those who think it's beneficial think it's risky (they explain this by reference to the halo effect):

Judgments of risk and judgments of benefit have been found to be inversely related. Activities or technologies that are judged high in risk tend to be judged low in benefit, and vice versa. In the present study, we examine this inverse relationship in detail, using two measures of relationship between risk and benefit. We find that the inverse relationship is robust and indicative of a confounding of risk and benefit in people's minds. This confounding is linked to a person's overall evaluation of an activity or technology. Theoretical and practical implications of this risk-benefit confounding are discussed.