Until you've offered up a few ideas of your own, you can't crap on anyone else's.
Other people’s opinions on your ideas will forever be a part of this process.
That said, colleagues are not critics.
They don’t get to sit on the sideline and analyze your work from afar. They are part of the team.
Anyone on the team must be contributing thinking and ideas to the mix BEFORE they start telling you what’s wrong with yours. Here's a thought...what if...how about...
If you have no ideas of your own, you forfeit your right to comment on other people’s ideas. This should be the rule.