Right now, the eugenics-happy alt-right are also climate deniers; but climate denial has a short half-life -- its undeniability will only grow, as the world gets hotter, more dangerous, drier, wetter, colder, stormier, more becalmed -- more uninhabitable.
Eventually, eugenicists will become climate believers, and that's when things could get very ugly. Charlie Stross's Happy 21st Century! predicts a time when nativism, xenophobia, and eugenics, along with the belief in the universal applicability of the social arrangements of lobsters, gets married to a willingness to make much of the planet uninhabitable to protect the fortunes of hydrocarbon barons.
This is not a pleasant prospect.
Think of it the backstory for a Fury Road-style exterminism, where Trumpism, Brexit, and Windrush are the early warning signs of a world of high border walls full of old, scared white people who have replaced the poor people who clean their toilets with robots.
Forget barbed wire, concentration camps, gas chambers and gallows, and Hugo Boss uniforms. That's the 20th century pattern of centralized, industrialized genocide. In the 21st century deep-learning mediated AI era, we have the tools to inflict agile, decentralized genocide as a cloud service on our victims.
Think in terms of old age homes where robots curate the isolated elderlies (no low-paid immigrant workers needed) and fail to identify their terminal medical conditions until they're too advanced to treat. People fed by vertical farms where solar/battery powered robots attend to the individual plants (thank you, Elon Musk's younger brother), food delivered by self-driving vehicles from lights-out warehouses, an end to high street shopping and restaurants and a phasing out of cash money.
Think in terms of a great and terrible simplification of our society that cleans out all the niches the underclass (which by then will include the struggling middle class) survive within.
Think in terms of policing by ubiquitous surveillance and social scoring and behavior monitoring. Think in terms of punishment by "community service"—picking up litter on starvation wages (and I mean, wages calculated to induce death through slow starvation), where if you fail to comply your ability to purchase the essentials of life using e-cash will simply stop working. Prisons where extensively drug-resistant TB runs rife as a discipline on the community service peons (as in: if you receive the sanction of an actual prison sentence, they won't need to execute you: 50% will be dead within 6 months). There's no state censor in this regime. Just a filter bubble imposed through your social media and email contacts that downranks anything remotely subversive and gently punishes you if you express an unconvenient opinion or show signs of noticing what's missing—the way you don't see people with dark skins or foreign accents any more, for example. The corporate social media will of course comply with state requirements for a safe and secure internet—if they want to stay in business, that is.
Happy 21st Century! [Charlie Stross/Charlie's Diary]