‘Books are the work of solitude, and the children of silence.’ Thus Marcel Proust. The writer is not the same person as the man. The writer, if any good, is a different person, a higher person or at least one who distils something more worthy than is evidenced in the blunderings and fumblings and inadequacies of the everyday character who shares the same skin. This was the basis of Proust's own blistering attack on Sainte-Beuve, to the effect that the critic (or so-called critic) substituted gossip for criticism and, incidentally, failed to recognize the genius of Baudelaire.
In philosophy we have our own Proustian tendency, in the unlikely form of Karl Popper, For Popper, the provenance of ideas is supremely unimportant—and so, by extension is the biography of their authors. A healthy corrective, one might think, to the present day culture of celebrity, even at the intellectual level, and to the flood of philosophical biographies and title-tattle. At a more serious level, it warns us that we should not treat a philosopher's ideas with suspicion because (just because he was a Nazi in his lifetime or she was a communist when she was young or the apostle of equality is a snob living high on the hoof or the advocate of open discussion anything but its practitioner.