Only a summary so far which seems to say in so many words that utilitarians are only thus because they never put themselves in the "innocent's to be sacrificed" category, so we should put utilitarians in that category first should the situation call for it, or else the belief is morally incongruent with reality
edit: here's the abstract
It is commonly thought that morality applies universally to all human beings as moral targets, and our general moral obligations to people will not, as a rule, be affected by their views. I propose and explore a radical, alternative normative moral theory, ‘Designer Ethics’, according to which our views are pro tanto crucial determinants of how, morally, we ought to be treated. For example, since utilitarians are more sympathetic to the idea that human beings may be sacrificed for the greater good, perhaps it is permissible (or, even under certain conditions, obligatory) to give them ‘priority’ as potential victims. This odd idea has manifold drawbacks but I claim that it also has substantial advantages, that it has some affinities to more commonly accepted moral positions, and that it should be given a significant role in our ethical thinking.
Essentially, just push against individualism and keep reminding them that context (social, economic, etc) going back decades will determine much of life. It's also helpful to try to remove binary good/bad morality from politics and explain the historical context of something, eg Russia/Ukraine, North Korea. That's laying a foundation for more complex moves later.
Just remember that you're not just explaining materialism, you are helping them unlearn brain worms. And that can take a long time with a lot of conversations