Is Plato right when he says that ignorance is the source of all evil? I live in
Let's start with a distinction. We may say that a situation is evil if it's sufficiently bad, whatever it was that brought the situation about—even if no one intended it. But we don't usually say that a person is evil unless they have evil intentions.
Start with evil people. In the kind of case that comes most easily to mind, ignorance isn't the issue. Sadly, there are people who just don't care. If what they do hurts someone else, it doesn't matter to them. In fact, some people take pleasure in other people's pain. I'm not sure that this kind of indifference and evil intention has much to do with ignorance. It's possible to know that something is wrong and not care. Plato may have thought otherwise, but it's not obvious that he's right.
It's pretty clear that the first kind of evil—objectively bad situations—can come about for all sorts of reasons, including sheer bad luck. Putting it down to ignorance is sometimes reasonable, but often isn't. And even when the bad situation comes about because of someone's ignorance, it may not be reasonable to expect the person to have known what they didn't know. But it seems a good bet that if people are ignorant, they may end up bringing about bad consequences simply because they didn't know what they needed to know to make things turn out better.
So maybe the thing to say is this: ignorance is one source of evil, but by no means the only one. It's plausible that if people are better informed, then various sorts of bad consequences will be less likely, though truly evil people can put knowledge to evil ends.