Here's one that I repeat alot that is probably pretty disagreeable-- I think people rate things WAY too leniently, particularly critics, whose job, I feel, should be to highlight the separation that is deserved. Things that even they would acknowledge as run-of-the-mill, deeply flawed, average guilty pleasures always get at least 3/5, anything remotely good is 4/5, and anything legimately solid/memorable/coherent/worth recommending gets 5/5 automatically. Everything from terrible to below average fall into the 0-3/5 range, and the full range of these numbers are barely ever used-- they all basically mean the same thing. You can tell that the critics can tell the difference between an okay 5/5 thing and one that's an outright masterpiece, but it's all lumped together, I guess so as not to upset anyone and be nice/positive as possible. It makes the number less useful when you're really looking for what critics see as the best things. And just about everyone who rates things seem to use this same type of scale! I guess it's a controversial opinion because I'm basically saying that critics are too easy-going and aren't nearly critical enough.
In my mind, your starting point for things that are damn solid, cohesive, memorable, have very few flaws, and wouldn't feel wrong to put on a recommendation list should only be around 3/5. When you see a solid/decent, but unspectacular thing like The Hurt Locker (and worse yet, sometimes formulaic Superhero movies) get the same rating as something like 2001:A Space Odyssey, it's just all kinds of wrong.
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Oh, here's a related one-- Neither expectations, nor what constraints/restrictions creators had to work under should have any bearing whatsoever on how something is assessed/evaluated. "What did you expect? It's a thing about _____" or "Yeah, but you have to remember that the creator had to juggle the needs of _____, _____, and ____, so what we ended up with is understandable" are meaningless caveats. If it works, it works, if it doesn't, it doesn't.
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Oh, and a good cause doesn't excuse a bad idea. The ALS Ice-Bucket Challenge, for example, was just a glorified modern version of annoying chain-letters on a global scale, and the fact that it was for a good cause doesn't improve that perception, for me, personally.
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Finally, I'm convinced that anyone who has ever called anyone a hipster is a terrible person. To just non-chalantly throw something baselessly accusatory and demeaning like that (You're basically telling them they're lying, greater-than-thou attention ******) because of someone's preferences..... how could they not be?