What's on others' trees does not affect a good researcher's results in any way. There are just too many tree-sites.

One tree with a great many mistakes copied from a badly compiled book, some genealogical files in a library, and some other mostly wrong sources, was up for a while concerning two of my ancestral lines. After some email exchange, at the owner's request I sent him complete hard-copy original-record documentation correcting the mistakes. The identical tree with all the mistakes remained on WorldConnect for another ten years. The whole thing was deleted a few years ago, but not before it and the mistakes were copied by many others.

The internet has massive quantities of wrong information about any subject you can think of, including genealogy. There is no correcting it, and no point in losing any sleep over it.