A few hiatus-breaking thoughts on whether moral realism is compatible with a strong belief in evolution and materialism. Briefly: moral realism is the idea that the moral status that attaches to certain actions is a feature of the universe ("real") and thus not open to interpretation--e.g. killing someone is always wrong, because that's just what killing is; evolutionary materialism is the idea that there exist only physical objects, some of which develop over time without any particular end in mind aside from continued survival. The tension, then, is that objective judgments of good and bad, which moral realism promises, have to actually exist somewhere, and the average materialist account can't specify exactly where. And this is most certainly true: most people's moral beliefs have a certain level of inflexibility (which is good), and most people can't give a coherent account of why they have those beliefs and not some others. But there are three potential issues with identifying this tension:
1. It always remains an option to bite the bullet--accept that unchangeable moral statuses are not compatible with materialism, and discard moral realism. This is the option of the philosopher Richard Rorty, who famously argued that there's not much of a difference, as a formal matter, between regular bourgeois western ethics and, say, genocidal ethics, just some slight differences in focus. Philosophical problems with this argument aside, it's not a bad position to take: you sacrifice the certainty of moral argument for a more passionate engagement in it: if our common, everyday moral language could easily be twisted into something we now find distasteful, we must be vigilant to ensure that doesn't happen.
2. There are forms of moral realism where it's less clear that this tension might be an issue. Utilitarianism, for example: moral judgments are real and objective measures of utility, but it requires no deep metaphysics to make them. There's always the issue that 'useful' or 'good' still requires some explaining, but if the argument is that in materialism it's difficult to make sense of abstract nouns, that seems to be a weaker position to hold. Nor is utilitarianism incompatible with rights-talk: all it requires is the belief that rights are not absolute trumps, which is a fairly widely held position in, say, contemporary human rights scholarship.
3. The third and quite likely possibility is just that the people advocating this combination of views are not moral philosophers and therefore don't have the argumentative dexterity necessary to see this problem. The issue, then, isn't one of deep incompatibility, but of listening to people who speak authoritatively far outside their area of expertise.