Why would their experience be relevant?

Partially, because experience in an area means one can understand the answer, but to a probably bigger part see below.

You could be nicer about it.

It read to me like they asked as if they know better than everyone else, and were ranting about others doing it wrong. But that was actually an assumption on my part, and may simply be their style, or even me completely misreading things. So thanks for calling me out on it.