Fortunately I haven't had any bad negative comments...just an occasional disagreement with my point of view, which is fine. That's why they make chocolate and vanilla. We can agree to disagree and still be cyberfriends.
But I would approve any negative comment except those that cross the decency line, and take it as an opportunity to win a new friend or change a mind.
Sometimes people say harsh or unkind things, then regret it. Approving the comment, and replying civilly to it, gives the commenter a chance to modify his/her original comment while preserving his/her dignity.
People who use unkind or overly sarcastic rhetoric tend to self-destruct anyway, so approving such a comment exposes it to the judgement of others, who will largely recognize it for what it is and simply disregard it.
When you open your talent or opinion to public scrutiny (especially worldwide) you should expect dissent, and develop a tough enough skin to deal with it and just move on.