It is not rational to ignore arguments because they were made by an awful person.

In academic philosophy there is a tendency to refer to "Heidegger's arguments and positions" as simply "Heidegger". (This is true of all philosophers, not just Heidegger). Popper, of course, would have been familiar with this; when I read that quote I got the distinct impression of "Heidegger's arguments are hollow and his positions are indefensible; please can we agree on this and stop discussing them?"