Why 罪人＝犯罪者のこと、not just 犯罪者？


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！]




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.

* * *

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

[code]

    俺のことを殴れ
    
[/code]

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

