For the majority of people who buy fish, I would be pretty confident in saying that PETA is probably right. Fish are not given the same respect as other animals and as a result they are commonly not properly cared for. If you read the list of suggestions for how to properly care for fish at the end of the article, most people fall short of providing even the baseline (bare minimum) of proper care; there are plenty examples of this on this site.
The fact that this forum is full of irresponsible hobbyist (despite all the knowledge/experience/information being readily available here) should tell you just how poor of a job the typical "hobbyist" does at caring for these creatures.
I'm obviously not for an outright ban on fish, but if you write PETA's concerns off as being ridiculous then you are being just as crazy as they are. Their concerns are valid, but I think their approach to the problem is too extreme.