Biased samples can be part of a planned procedure and are generally more amenable to numeric adjustment, to remove bias.
OTOH, anecdotal evidence can include, and more often does,
events that are more isolated, and hard to adjust, and are
hard to fit in study.

In any case we use all kinds of evidence, we just need to try
to piece it together the best we can.
I actually am more concerned with a biased reporter than
I am with a biased sample. It is very difficult for me to adjust
for the POV of the reporter.

You seem very convinced of your position, an your
position is self evident, I will waste no more time with you.