Lifetime prevalence of oppositional defiant disorder (in the US) is about 11% for men and 9% for women, from a study of 3200 adults in 2007. There are quite a few people who will go contrarian "just because". So 1+1=2, yes? In binary it is 10, there is no 2 in binary, so not always!
Looking at a whopping 3 amplifier polls, it does seem like 10% is a good number to start with for contrarians on the site.
Opinions are asked for, so a better way to frame the OP question would be "Who are the people who vote poor on highly accurate equipment..." Accurate only equals good if you value accuracy. As has been pointed out by Digby, they might be using value for money. They might be super picky about one thing. They might love tube amps and no other. They might downgrade for "ugly".
To the extent these (self selected and not at all random) polls are useful, they are useful in the aggregate, in a wisdom of the crowds way. Subset analysis is usually not worth the time. For this data, I can see some value of paying attention to the split among the positives (for highly rated) or negatives (for the low rated). Given 2 results of 80% great/10% fine and 40% great/50% fine... there is probably a reason for the difference. So I might dig in to find out what people are saying, if I were in the market and considering those two bits of equipment. Maybe the reason for the "fine" won't bother me, maybe it would.
I would probably not look for amplifiers, since I assume the correlation between ratings and SINAD is pretty high. For speakers, more likely to investigate the split, if I came across one when reading reviews of potential speakers. Not very likely, but more likely.