yes; people put all sorts of misinformation online, because they think it's right, or because they don't proofread what they've written ,or because they've just copied it from another online family tree that's wrong. The trickiest ones to spot are the ones that are mostly correct.
That said, are you certain you're right and the other one's wrong? I have occasionally been in this position and realised that I was the one with the wrong end of the stick.