Right, comparisons are fine. They compete in the same space against each other, so it's helpful to compare them in certain areas. I don't take issue with comparisons and I don't take issue with knocking the review scores down because of the various problems/missing features. What I do take issue with is saying things like "they're bad tablets" because they don't compare favorably to a specific product on a specific feature. I take issue with "They should be judged by the same standards". Apple doesn't get to set what standard tablets are judged by.
For example, you could argue that Apple's browser is more stable, but Google's browser has more features and a nicer interface. Why does Apple necessarily win that comparison? If you are only concerned about stability, sure, but that's just one consideration. Google's is plenty stable for me and the interface makes it better overall IMO. Or, similarly, the Playbook lacks an email client, but it has the Bridge software. I've never used an email client on my tablet or phone, I just use gmail, so that's not necessarily a big deal. Now, I'm just one person, but that's exactly the point. Just because the occasional crash or missing piece of software completely ruins your experience doesn't mean that it ruins it for everyone. These other tablets shouldn't be "trashed" just because they have different pros and cons, and if someone can't recognize that there are pros and cons to every product then they're just blinded by fanboyism.