Maybe because the discussion is not of very high quality? Look how many downvotes there are already, it is an emotional topic and yes, even here people are having problems with maintaining a civil debate about a controversial topic. And others don't want all that flame war here, so they flag it, simple as that.
The mechanism of downvoting is supposed to remove low quality posts. If someone if uncivil, downvote or flag them. Soon enough they'll get the hint or be warned.
> others don't want all that flame war here
That doesn't make sense. If you don't want to participate, then ignore the post. actively preventing others participating is something else - I think "censor" is more appropriate in that case.
the front page isn't limited. Hit "next" and you see as many more posts as you like. Most front-page posts are tech related, we are far from being overrun with controversial posts.
