Not all genealogists are created equal. I am not trying to sound judgemental but you are going to find some information that just is not correct put out on sites like Ancestry.com. I am very frustrated by this sort of carelessness especially by people who are always offering information to other people.
If you haven't come up against this yet, you will. You can't remove their information you can only ask them to correct what they have put up. Some people will not change the information even if you offer irrefutable proof that what they have is incorrect. It is very frustrating.
What makes it worse, is if the people they have wrong are your ancestors but not theirs. Why do they have your ancestors on their genealogy if they are not related to them? They may be connected at some point and they decide to add information to collateral people in their genealogy.
People are always asking me why I have my family tree hidden on Ancestry. I will share it with people who are related but I have spent years collecting this information and I cherish it.
Genealogy is not a fast process, it takes years of dedication. Information needs to be sourced and proven. It is easy to jump to wrong conclusions, it happens but those things we don't put out as facts until we are sure or as sure as we can be.
If you are not going to make sure that your information is not 100% sourced and correct, keep it to yourself please and don't muddy the water with guesses. Okay, I am done ranting for the day.