Presenting the opposing viewpoint actually strengthens your own argument because it shows you to be credible, fair-minded and unafraid.
You promised your reader that you would talk about certain ideas in a specific order in your thesis statement and in your POPs. In your body paragraphs you are making good on that promise.
In the multiple-paragraph essay, the thesis statement announces to the reader, “I am going to be discussing something very specific and very important and THIS is what it is.”
A good hook demonstrates that you know your audience and that you understand what they care about. More importantly, it makes the reader want to keep reading.