Is it really a bad idea? Or do you not like the person? Or do you wish you had thought of it first? Or is it going to help someone else?
These feelings are all natural and valid to have, but letting them get in the way of a good solution is unprofessional and might turn against you if it causes you to ignore an idea that would benefit you down the line.
The trick to not let your emotions have a say is to define what a “good idea” is in your particular context then see how all the ideas put forward hold against that definition. Don’t second guess, don’t anticipate, don’t predict – just measure and make your decision based on that.
You win when the right idea is found, so if it’s found by someone else you win twice because you didn’t even have to do any work.