I. -지 말다
There is no universal Korean equivalent to the "don't be an N" construction.
We can consider the following cases separately.
- There is a Korean equivalent to "N" and the imperative concerns a particular occasion.
For example, "Don't be a fool" said to someone who got frustrated and began to cry where crying would do no good. Here, the most likely thing is:
바보처럼 굴지 마. (Don't behave like a fool.)
Of course you cannot say this to just anyone, from consideration of respect, etc. (But nor could you in English.)
If you are talking "up," it may become:
바보처럼 굴지 마세요.
It may seem incongruous, but grammar does not forbid it any more than it does:
Mr. President, don't be an idiot!
Another formulation may be:
바보짓 하지마. (Don't do a fool's act.)
- There is a Korean equivalent to "N" and the imperative concerns some longer period than a single occasion.
For example, someone might have told Caesar not to be a Sulla (in reference to the latter's long term policy or career). This is likely to be:
술라가 되지 마시오. (Don't become a Sulla.)
If you wanted to allow some bloodshed, but not a wanton amount, this might be:
술라가 되지는 마시오. (Don't go so far as becoming a Sulla.)
술라는 되지 마시오.
- There no Korean noun equivalent to "N".
For example, a "wet blanket" does not seem to have a ready noun equivalent in Korean. In this case you would probably find the nearest verb equivalent. For example:
분위기 깨지 마. (Do not break the mood.)
I guess this is no different from what you would do in English. If there is no ready noun for some concept, you wouldn't try to invent one so as to say, "Don't be an N."
One clarification. I don't mean to suggest that the "N처럼 굴지 마" formulation is unavailable for "longer term" imperatives. For instance, taking the person in item 1 aside, who has done some useless crying, you may say, "바보처럼 굴지 마," meaning henceforward don't do it.
But this is no different from any "per occasion" imperative serving for "long term" as well. For instance, "Don't push that button," might serve for either.
II. -어하지 말다
Per your question in the comments, some words on adjectives.
Both verbs and adjectives take -지 말다
"-아/어하지 마세요" is not a (straightforward) way to turn adjectives into a prohibition. You may know that the "base form" of a Korean adjective looks just like that for a verb. For example 길다 (to be long, an adjective), but 걷다 (to walk, a verb).
Therefore, the same "-지 말다" (base form of "-지 마세요") is good for verbs and adjectives alike. For example.
오지 말다 (not to come, containing the verb 오다)
늦지 말다 (not to be late, containing the adjective 늦다)
늦게 오지 말다 (not to come late, containing the verb 오다 as modified by the adverb 늦게)
Components of -아/어하지 말다
What is then "-아/어하지 말다"? It is a compound made of "-아/어하다" and "-지 말다." That is to say, a two-step process.
"-아/어하다" turns an adjective into a verb meaning "to have/exhibit the attitude denoted by the adjective." For example, from
좋다 (to be good)
예쁘다 (to be pretty)
좋아하다 (to like)
예뻐하다 or 예뻐 하다 (to consider pretty, adore, dote on)
On spacing, 좋아하다 has solidified into a single word and is never separated while, 예뻐 하다 being two separate words, the space in it is optional.
You now have two verbs, on which you can perform the "-지 말다" operation to get:
좋아하지 말다 (not to like)
예뻐하지 (예뻐 하지) 말다 (not to consider pretty, etc.)
However, there may be a semantic interference with applying "-지 말다" to many adjectives. Consider:
젊지 마오 (don't be young, from 젊다)
예쁘지 마오 (don't be pretty, from 예쁘다)
바쁘지 마오 (don't be busy, from 바쁘다)
Just when would you say such a thing? Maybe never. That does not mean these sentences are grammatically ill formed. They would do fine in poetic or playful context, e.g. a lover telling the beloved not to be so ravishing.
From this semantic consideration, someone may have told you that -지 말다 applies to verbs but -어하지 말다 to adjectives. But if there was any suggestion of equivalence, that was wrong.
This can be readily seen if you consider:
아프지 마오 (don't be in pain or sick, from the adjective 아프다)
아퍼 하지 마오 (don't be pained, give way to pain, or indulge it, maybe after being jilted)
The first item is the straightforward equivalent to "걷지 마오" (do not walk) while the second item does something more complex.
Perhaps the more critical thing to know is that the "-어하다" and therefore "-어하지 말다" form are not available for just any adjective. The following do not exist.
늦어 하다. 늦어 하지 말다.
젊어 하다. 젊어 하지 말다.
By the way I see no semantic interference in "아프지 마오" (you can say it without being poetic etc.). So with "늦지 마오."
Semantic Considerations for Adjectives of Emotion
From the examples above, you may have noted that -아/어 하다 (and therefore -아/어 하지 말다) as applied to an adjective may change the meaning in subtle, unpredictable ways. It is similar to reflexives in French or German not always coming out the way you might expect from the meaning of their straight transitive counterpart.
To 기쁘다 (glad), 슬프다 (sad), 무섭다 (fearful), and other adjectives of emotion, however, -아/어 하다 does something fairly predictable, which is to externalize the emotion or put a little distance. For example, compare:
네가 상을 타서 나는 기뻐. (Because you won the prize I am glad.)
네가 상을 타서 아버지가 기뻐 하셔. (Literally: Because you won the prize father is doing/having/acting/showing gladness.)
The second line, however, really means that father "is" happy. That is to say, a Korean speaker would say "아버지가 기뻐 하셔" exactly when an English speaker would say "father is happy."
You would never say of yourself in the present and for the present occasion:
네가 상을 타서 나는 기뻐 해.
But you can say:
나는 작은 일에 기뻐 해. (Laterally: I do gladness on small things.)
meaning that it is true of yourself in general that small things make you glad.
네가 상을 탔다고 하기에 나는 많이 기뻐 했어. (Lit: Because it was said you had won the prize, I did etc. gladness.)
suggesting (though not requiring) that you are perhaps no longer glad because e.g. what you'd heard turned out to be false reporting.
In both these cases, you as speaker are distancing yourself from you as the thing spoken of.
Conversely an omniscient narrator of a novel might say:
철수가 상을 타서 영희는 많이 기뻤다.
This removes the usual distance between the speaker and the person spoken of under 기뻐 했다.
And yes, you would say:
슬퍼 하지 마 (Lit. don't do etc. sadness),
But really meaning, "Don't be sad."
This is just another instance of the distance required when the speaker and the person spoken of are not identical.
I realize it's rather complex.