I don't follow this. If we meet a scientist who is a Marxist, or a Democrat, or a libertarian, or a Republican, or whatever, we don't point out that there is no empirical proof that any of those political programs would achieve its desired aims, and that no true scientist would hold political beliefs. We accept that political decisions are made on different (some would say weaker) evidence that scientific decisions. More generally, there are many questions that the methods of science can't be used to answer.
I don't follow this. If we meet a scientist who is a Marxist, or a Democrat, or a libertarian, or a Republican, or whatever, we don't point out that there is no empirical proof that any of those political programs would achieve its desired aims, and that no true scientist would hold political beliefs. We accept that political decisions are made on different (some would say weaker) evidence that scientific decisions. More generally, there are many questions that the methods of science can't be used to answer.