Personally, I don't have a problem with people being negative. 99% of startups fail, and I think it's worthwhile reminding people of that every now and then. Hacker News shouldn't live in some magical land where everyone is going to make the next billion dollar company.
If you truly, genuinely, believe in your idea then you can take the negativity in your stride. There will be plenty of constructive feedback buried in there somewhere. If you can't take a little negativity directed towards your project, then maybe you're in the wrong business. And maybe it is a bad idea. Sometimes it's best to find that out and move onto a new idea, rather than bathe in the vague compliments of your peers.