Well, we can't really know everything he said is valid (he might be mistaken or deceived, for example) but certainly some of it is. But one doesn't need Snowden to know government will expand its powers if allowed to do so. You don't need Snowden, you just need a good history book and a bit of thinking. Snowden revelations showed how bad exactly it has gotten. But you could predict that it's going to get bad just because the government has been given wide powers and no substantial control over them. There's no way it would not go bad, it always does.