I'd love to explain the basic position, and tell me where you disagree with it. This is the basic position:
1. Intelligence can be created, because there is nothing "special"/"magical" about humans, and our intelligence was eventually created.
2. At some point, humanity will create an "artificial general intelligence". (Since we'll just keep improving science and technology, and there's no fundamental reason why this won't eventually allow us to create an intelligence.
3. "Artificial general intelligence" basically means a machine that is capable of achieving its goals, where the goals and methods it uses to achieve them are general. I.e. not "is able to play chess really well", but rather "is able to e.g. cure cancer".
4. For various reasons, once we have an artificial intelligence, it will likely become much smarter than us. (There are many reasons and debates about this, but let's just assume that since it's a computer, we can run it much faster than a human. If you dispute this point, we can talk about it more).
5. Something being much more intelligent than us means that, in effect, it has almost absolute power over what happens in the world (like we are basically all-powerful from the vantage point of monkeys, and their fate is totally in our hands).
6. (This is, I believe, the main point): Something being "intelligent" in the sense we're talking about doesn't say anything about what its goals are, or about how its mind works. We're used to everything that's intelligent being a human being, therefore the way our mind works is basically the same across every human. With an artificial intelligence, it will work completely differently from our mind. So if we "tell it" something like "cure cancer", it won't have our intuition and background knowledge to understand that we mean "but don't turn half the world into a giant computer in order to cure it".
7. Combine the two points above, and you get the large idea - whatever the goals of the AI will be, it will achieve them. Its goals won't, by default, be ones that are good for humanity, if only because we have no idea how to program our "value system" into a computer.
8. Therefore, we need to start working on making sure that when AI does come, it's safe. Even if we create an AI, the "extra" problem of making it safe is both hard, and we have absolutely no idea how to do it right now. We have no idea how long AI will take, or how long figuring out safety will take, but since this is a humanity-threatening problem, we should devote at least some resources to working on it right now.
That's it, that's the basic idea. I'd love to hear which part you disagree with. I totally understand that not everyone will agree on some of the final details like, e.g., how many resources we should effectively devote right now (you might even claim it's 0 because anything we do now won't be useful).
But I think the overall reasoning is sound, and would love to hear an intelligent disagreement.