A perfect example is this thread: whoever posted this thread didn't pay much attention to the responses to the previous, practically identical, thread. If s/he had understood the "affinity, filtering & reproduction" comments, s/he would/should not have bothered posting the remarkably long & misguided "second proof". I expect to see a third post, which will say the same thing and miss the hundred counter-proof posts previously posted.
I disagree. Those who are immune to learning lose nothing. Those who already know everything lose nothing. But many people between these extremes learn both from the content of the debate and from the process of forming and expressing opinions.