I’ve noticed that many defenders of the hateful policy of separating families at the US border claim that this is “necessary” if they are going to be detained.

That’s straightforwardly false.

When Japanese-Americans were (utterly immorally, and utterly hatefully) “detained” in internment camps during the Second World War there was no deliberate policy of breaking up families; they were interned together. (In appalling conditions.) There is thus nothing preventing the families who are currently crossing the border from similarly being detained together. To separate them is thus a choice, not a necessity.

When you defend a policy that is in one respect worse than the atrocious forcible internment of Japanese-Americans you should pause to consider what sort of a person you are.