

Well, you’re denying people certain basic freedoms based on who their parents were. Not all countries provide citizenship based on ancestry, and this means that denying birthright citizenship can lead to statelessness, which is very dangerous for those people. So for them, it is a requirement for a basic and normal life free from state violence.
More accurately, they’re both separate descendants of ethnonationalism which was a popular ideology at that time. And still today, evidently, though it seemed to be in decline for a bit during the post-war period.