It's a genuine problem and has been growing gradually worse for a while. I think the cause is simply growth. When a good community grows, it becomes worse in two ways: (a) more recent arrivals don't have as much of whatever quality distinguished the original members, and (b) the large size of the group makes people behave worse, because there is more anonymity in a larger group. I've spent many hours over the past se…
Sometimes saying an idea is pointless is positive feedback, there are a lot of people here that 'launch a startup' which basically means some half-assed website that does something utterly pointless and then expect the community to be like some kind of benevolent uncle and pat them on the back and say what an awesome idea and execution. Many many ideas really are pointless and negative criticism is very much a part o…
A particular example of a recent top-voted comment comes to mind (I'm not going to identify it because my purpose is not to name and shame), which was full of perfectly legitimate and constructive criticisms, but the tone of the comment was, well, mocking.
And what's the point of that? Making legitimate criticisms and dressing them in derisive language is a great way to raise an army of contempt against someone, but why?
If you want the target of your criticism to take the criticism into account, you need to express it civilly. You don't need to find positive things to say, or even claim that you think there's a kernel of good idea to be found (although genuine compliments are great too, of course). All you have to do is be polite and respectful. Imagine that the creator of what you're criticizing has just shown it to you excitedly. Read your comment, and decide if what you're writing is something that an acceptable member of society would say to that person face to face. Not the content, but the actual words.
And if you don't want the target of the criticism to listen to you? Then maybe you should just keep your thoughts to yourself.