That just isn't true. Critics often aren't artists, musicians, actors, etc.....you can have a keen sense of art without trotting around your degree to shove in everyone's face just as you can have perfect pitch and never have studied music. A critical eye is a speciality in itself...and artists often don't own it themselves. Having said that, I also would say that no one is necessarily who they say they are on the Internet (yes, it's been said before...because it's true) so don't take anyone's criticism at face value (unless you want to).