There are two mindsets you can take while judging the output from a brainstorm; A positive mindset where you look for great thoughts, and a negative mindset where you attack and eliminate thoughts that aren't great/ have issues (most brainstorms are judged using the negative mindset).
The less helpful mindset is the later. There are multiple issues with this. Most ideas, concepts, and territories that arise in brainstorms aren't fully developed and are easily attacked. Most concepts and territories can be dismissed due to them not being an actionable idea. Any innovative idea that challenges you and the team to think differently can easily end up on the floor. And when you start attacking ideas it's easy to gain momentum and dismiss thoughts in rapid fire. This mindset will result in a small handful of mundane ideas.
The other more productive mindset is to seek out greatness. To identify any thoughts that are exciting/ intriguing/ interesting. This is where you should listen to you gut, get excited and see opportunities. Don't get hung up on any issues or weaknesses (at this stage).
Make love, not war. You'll end up with more amazing and innovative ideas.