If the point of the site is to host a blog where people can debate things, well surely, they can respond to the blog in the comments section? Some of the most lively debate I have seen online has been in the comment section of blogs. Don't make it complicated for yourself. You have a domain name? Pop a wordpress blog on it (DM me and I can give you the details of someone who can put one together for you) but the issue you will have is traffic - I imagine. Best to pop Twitter on there too. Generating traffic to a blog is not a quick process. If you want to do that effectively, you would probably be best to engage an online PR person.