Its 100% necessary to be able to read performance levels of individual players for such difficult and performance demanding content.
Taking a screenshot of someone's poor performance and harassing them publicly about it, which is YoshiPs' primary concern, is a completely different matter with no correlation.
In my 15 years of raiding in WoW with damage meters and parses and all of that I have never seen a single person do that, even the most immature people. YoshiP is completely irrational on the subject.