Why 罪人＝犯罪者のこと、not just 犯罪者？

Question

I was reading a guide to 刑事ドラマ and 時代劇場. Most of the definitions follow the format:

真犯人：本当の犯人。 盗人・盗賊：他人の物を盗む人。

However for one or two words such as 「罪人」 it says:

罪人：犯罪者**のこと**。例：友人のことを罪人扱いするなんてひどい！

My 大辞泉 dictionary tells me 罪人＝罪を犯した人。つみびと。- ie a person not a "こと”

What is the nuance of こと here?　Why does it not just say:

罪人：犯罪者 [例：友人のことを罪人扱いするなんてひどい！]

Answer 1

I think there is little difference between 犯罪者のこと and 犯罪者. I think user54609's explanation is nice.

罪人：犯罪者のこと basically means 罪人は犯罪者のことだ, 罪人は犯罪者のことを指す or 犯罪者のことを罪人という. You explain 罪人 by rephrasing it saying 犯罪者. つまり～のこと is a very frequent expression used to rephrase what just has been said.

AはBのことだ basically means A means B or A refers to B. You can't expect A is a kind of こと because some nouns work like verbs by connecting two phrases in some way. e.g. AはBの予定だ, AはBの意味だ, AはBの感じだ, etc. When you put them into English, they become A plans B, A means B, A seems B, etc. And AはBのことだ is similar to them. It not A is a koto of B, but A kotos B. i.e. A refers to B

こと might originally mean something like 言うこと/ことば or 考えること. It has become an abstract marker for objects related to mental activities. e.g. 友人のことをどう思う, 友人のことをどう扱う, 友人のことをどう考える, 友人のことをどう呼ぶ etc.

I think のこと should be redundant because the verb is already a mental activity and require a mental object. But it's just required for some verbs and can be omitted for some else verbs, just like のところ is required for some verbs, even if the verb obviously requires a locative object.

(人)のことを言う and 話す are more likely to be used with ～のこと, but in ～のことが好き and ～のことを指す, こと can be omitted. I don't think they make big difference.

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Maybe it's off-topic, but I think I sometimes saw こと used for non-mental-action verbs. e.g.

俺のことを殴れ

I don't know what the nuance is, when and how it is used. But I guess it might be similar to 扱う.

Answer 2

In the 大辞泉 context, the distinction of a person from "こと" seems like separating the criminal person from the guilt. Here, "こと" represents an abstract concept of guilt or the fact of the crime.

In the 「友人のこと」 context, the noun "こと" is used in a quite different way as just a cushion. The combination 「X のことを Y 扱いする」 is common, but it has almost the same meaning as 「X を Y 扱いする」.

Answer 3

I think the thing lies in the clearer use-mention distinction Japanese has. The letters 「罪人」 are not by themselves a 犯罪者, but it refers to 犯罪者, thus the のこと.