If you go to http://stackoverflow.com/faq#close, you get
As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or specific expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, see the FAQ for guidance.
which links to http://stackoverflow.com/faq#close itself. Can't the link go to something with more than one paragraph on what's meant by "not constructive", and why they aren't appropriate for Stack Overflow / Stack Exchange sites?