I feel that too many people copy information from other trees, assuming that if it's there it must be true. There are plenty of articles about being wary of bad information in family trees and, if people don't want to bother to check the facts, then I say that's their problem.
Probably the best you can do is put notes on these people in your tree, explaining why you think your information is correct and the other is not. But, the bottom line is that you're probably swimming against the tide. Once an error gets started, it's probably impossible to stop, and the people who have the error in their trees don't care.