Tell them they’re wrong. Tell them you have a better idea. Back up your idea with some made up evidence based on opinion. Make sure they know you’re smarter about whatever topic you’re talking about. That’ll work! That person will never want to share an idea with you again.
Every time you shut down someone’s idea it’s like poking a bear. Sure you can get away with it the first time and maybe the second, but sooner or later if you keep poking, the bear is going to eat you.
Don’t strive to be “right” in conversations, that’s your ego coming through. Be confident in yourself, so confident in fact that you let others be right. Then more and more you’ll find others wanting to share their ideas with you.