Yes, much of what is written about him is fictional, though we can be fairly sure he did exist. I'm only guessing, based on some long-ago reading of Plato and of the sophists Socrates is said to have argued with, that a clever person would not have too hard a time finding the flaws in their theories and flummoxing them. It's likely enough, though, that Plato conflated stories and neatened them up, if not actually making them up, for his own purposes. But the world is complicated and chaotic, so it's not really all that hard to find a contradiction or a fault when someone tries to reduce it all to a grand over-arching theory, which is something philosophy tries so often to do.