Local talent shows at fairs, schools and community events are not for audiences to boo but applaud. It takes effort and courage to get in front of people and unless a performer gets up there only to be rude to the audience then the correct behavior after a performance is to applaud. If you weren't thrilled with the performance, applaud lightly. If the performer took your breath away, give that talented person a standing ovation. But no x's. No even thinking about it. Enjoy it for what it is; don't compare it to Hollywood or Broadway.
And for those of you who put yourself on stages in your local areas, Thank you! Thank you for being willing to put yourself out there like that so the rest of us--who don't live in LA or NYC--have live performances to enjoy!