The only thing I knew about Popper, before I read your post, was his philosophy of science, which as my post above describes, was very astute and truthful. I'm delighted to read of his condemnation of Marx and Hegel. There are many good and orthodox people who admire much of what was written by Plato, although this doesn't necessarily negate Popper's criticism. However, the other two are real nasties and many people with a far broader and deeper grasp of these issues would regard Hegel as the most iniquitous. I think, if my memory serves me well, Hegel would be the primary source of moral relativism. If one can judge a man by his opponents, this all reflects well on Popper.