Okay, imagine you have two friends, and they never get along. One of them always criticizes the other because they never agree on anything. One day, the first friend suggests an idea, and the second friend loves it! However, just because the first friend suggested it, the second friend doesn't want to agree with them.
This is called reactive devaluation. It means that if someone you don't like or trust suggests something, you automatically assume it's not a good idea, even if it actually is a good idea. It's like when your little sister says she wants to play with your toys, and suddenly you don't want to play with those toys anymore, just because she asked!
Reactive devaluation can cause misunderstandings and stop people from collaborating and making good decisions. It's important to try and evaluate ideas on their own merits, regardless of who suggests them.