+1! Slant.co works great because many "not constructive" questions are on the format "which alternative among $x is best for $y?" However, the site seem to be lacking in polish. For example, it doesn't remember your login and the procedure for updating and commenting on viewpoints is convoluted. Plus, there is no timestamps anywhere so it's hard to see what is going on on the site. Stackoverflow is much better from a usability perspective.

I was about to post the same thing. I think Slant is exactly the platform we're talking about here and it's already good to go!