The concept of "deserve" can be harmful. We like to think about whether we "deserve" what we get, or whether someone else deserves what he/she has. But in reality there is no such mechanism. I prefer to invert "deserve" into the future: deserve your luck by exploiting it.

Of course, "deserve" can be a useful social mechanism to increase desired actions. But only within that context.

(Thinking about this for a bit, I noticed that it was more fruitful for me to think of "concepts that are often used unskillfully" rather than "bad concepts" as such. Then you don't have to get bogged down thinking about scenarios where the concept actually is pretty useful as a stopgap or whatever.)

Bad Concept: Obviousness

Consider this - what distinguishes obviousness from a first impression? Like some kind of meta semantic stop sign, "it's obvious!" can be used as an excuse to stop thinking about a question. It can be shouted out as an argument with an implication to the effect of "If you don't agree with me instantly, you're an idiot." which can sometimes convince people that an idea is correct without the person actually supporting their points. I sometimes wonder if obviousness is just an insidious rationalization that we cling to when what we really want is to avoid thinking or gain instant agreement.

I wonder how much damage obviousness has done?

Implicitly assuming that you mapped out/classified all possible realities. One of the symptoms is when someone writes "there are only two (or three or four...) possibilities/alternatives..." instead of "The most likely/only options I could think of are..." This does not always work even in math (e.g. the statement "a theorem can be either true or false" used to be thought of as self-evidently true), and it is even less reliable in a less rigorous setting.

In other words, there is always at least one more option than you have listed! (This statement itself is, of course, also subject to the same law of flawed classification.)

"Your true self", or "your true motivations". There's a tendency sometimes to call people's subconscious beliefs and goals their "true" beliefs and goals, e.g. "He works every day in order to be rich and famous, but deep down inside, he's actually afraid of success." Sometimes this works the other way and people's conscious beliefs and goals are called their "true" beliefs and goals in contrast to their unconscious ones. I think this is never really a useful idea, and the conscious self should just be called the conscious self, the subconscious self should just be called the subconscious self, and neither one of them needs to be privileged over the other as the "real" self. Both work together to dictate behavior.

"Rights". This is probably obvious to most consequentialists, but framing political discussions in terms of rights, as in "do we have the right to have an ugly house, or do our neighbors not have the right not to look at an ugly house if they don't want to?" is usually pretty useless. Similarly, "freedom" is not really a good terminal value, because pretty much anything can be defined as freedom, e.g. "by making smoking in restaurants illegal, the American people have the freedom not to smell smoke in a restaurant if they don't want to."

The word "is" in all its forms. It encourages category thinking in lieu of focussing on the actual behavior or properties that make it meaningful to apply. Example: "is a clone really you?" Trying to even say that without using "is" poses a challenge. I believe it should be treated the same as goto: occasionally useful but usually a warning sign.

There is a cultural heuristic (especially in Eastern cultures) that we should respect older people by default. Now, this is not a useless heuristic, as the fact that older people have had more life experiences is definitely worth taking into account. But at least in my case (and I suspect in many other cases), the respect accorded was disproportionate to their actual expertise in many domains.

The heuristic can be very useful when respecting the older person is not really a matter of whether he/she is right or wrong, but more about appeasing power. It can be very useful to distinguish between the two situations.

Within my lifetime, a magic genie will appear that grants all our wishes and solves all our problems.

For example, many Christians hold this belief under the names the Kingdom, the Rapture, and/or the second coming (details depend on sect). It leads to excessive discounting of the future, and consequent poor choices. In Collapse Jared Diamond writes about how apocalyptic Christians who control a mining company cause environmental problems in the United States.

Belief in a magic problem solving genie also causes people to fail to take effective action to improve their lives and help others, because they can just wait for the genie to do it for them.

I am not sure I am comfortable with the idea of an entirely context-less "bad concept". I have the annoying habit of answering questions of the type "Is it good/bad, useful/useless, etc." with a counter-question "For which purpose?"

Yes, I understand that rare pathological cases should not crowd out useful generalizations. However given the very strong implicit context (along with the whole framework of preconceived ideas, biases, values, etc.) that people carry around in their heads, I find it useful and sometimes necessary to help/force people break out of their default worldview and consider other ways of looking at things. In particular, ways where good/bad evaluation changes the sign.

To get back to the original point, a concept is a mental model of reality, a piece of a map. A bad concept would be wrong and misleading in the sense that it would lead you to incorrect conclusions about the territory. So a "bad concept" is just another expression for a "bad map". And, um, there are a LOT of bad maps floating around in the meme aether...

This one is well known, but having an identity that is too large can make you more susceptible to being mind killed.

Death is good.

"Harmony" -- specifically the idea of root) progressions -- in music theory. (EDIT: That's "music theory", not "music". The target of my criticism is a particular tradition of theorizing about music, not any body of actual music.)

This is perhaps the worst theory I know of to be currently accepted by a mainstream academic discipline. (Imagine if biologists were Lamarckians, despite Darwin.)