You don’t need to concede to their belief and subsequent policies if they aren’t grounded in reality, like on immigration. You provide a counter narrative grounded in reality that actually address their needs and concerns, real or perceived.

The Republican narrative on immigration is that immigrants are criminals, bringing crime and drugs into our country to kill our citizens, steal jobs, and exploit welfare, so we need mass deportations. None of that is based on reality.

US citizens are responsible for smuggling in drugs. Immigrants are responsible for less crime per capita than US citizens, use much less welfare than citizens, and contribute far more than they use. The underlying fear is cost of living and safety. So a counter narrative that both points out the realities of mass deportation, aka concentration camps, and provides real solutions to the problems, would absolutely capture those voters and fracture the Republican base.

Those real solutions would include legalization of illegal immigrants to stop companies from exploiting both them and citizens with a two-tier immigration system, increasing taxes on corporations and the wealthy to pay for universal social services, systemic solutions to addiction and homelessness, and increasing security to catch smugglers at points of entry. All of which are popular. You address their fears, improve their material needs, and point out how terrible the oppositions ‘solutions’ are, all without conceding to the Republican framing based on racist lies.

In fact, many progressive policies are popular across the board, including Republicans and independents.