Demographic replacement, or demographic death, is not an expression used exclusively by white identitarians, but occurs elsewhere, in other contexts:
  https://www.timesofisrael.com/pa-premier-without-two-state-solution-israel-will-suffer-demographic-death/

“PA premier: Without a two-state solution, Israel will suffer ‘demographic death’. Mohammad Shtayyeh says Palestinians are majority between Jordan River and Mediterranean for 1st time since 1948; slams US envoy’s comments on Palestinian rights; hosts Meretz group. If a two-state solution is not achieved, Israel will suffer “demographic death” and will not be able to exist as a democratic state, Palestinian Authority Prime Minister Mohammad Shtayyeh said on Tuesday. “Israel stands today before a big challenge — either the two-state solution or a demographic death,” Shtayyeh said in a speech at a meeting of Socialist International, an organization that brings together socialist parties around the world, at the upscale Carmel Hotel in Ramallah. “For the first time since 1948, the demographic balance is in favor of the Palestinians. Between the Jordan River and the Mediterranean Sea, there are 6.8 million Palestinians — 3 million in the West Bank, 2 million in Gaza and 1.8 million in 1948 [Israel]. The Israelis are 6.6 million. The Palestinians are 200,000 more than them. “Either the two-state solution or a demographic death; either the two-state solution or no democratic or Jewish state; either the two-state solution or a racist regime in practice and law; either the two-state solution or no peace,” he declared.”

     There we can see that population increase is being proposed as a demographic weapon, and poses an existential threat to the existence of Israel, as strong nationalist leaders recognise:
  https://www.middleeastmonitor.com/20180419-netanyahu-israel-is-exposed-to-existential-threats/
  https://www.haaretz.com/1.4802179