Usage of も in そんなこともないけど


Context: a guy has invited his girlfriend over to study, and the girlfriend
finds a dirty magazine. The following exchange takes place:

> 男 : 香奈さん? 今日はテスト勉強しにいらしたのでしょう？  
>  女 : 何が勉強だし! どうせ千秋はこういうことばかり考えてたんでしょ！  
>  男 : そんなこと **も** ないけど…

Why did he say も here instead of saying そんなことないけど or something similar? I
can't quite figure out in what sense the particle is being used. It doesn't
seem to me a case of it being used in the sense of "even," or trying to show
how big of a thing something is. It also doesn't immediately make sense to me
for it to be in the sense of "also"; in that case it would mean "that's not
the case" (in addition to other things not being the case), but the only way I
can make that make sense is if I assume what he means is "I didn't invite you
over for that, but I may not have invited you over to study either."




The も is used in the sense of...

> も 〘副助〙*  
>  ⓬ さりげなく取り立てて、文意をやわらげる。...  
>  ㋐《多く、文末表現に使って》一歩引く気持ちで、その判断をやわらげる。...  
>  「その件なら知らなく **も** ない」「そんな感じがしないで **も** ない」  
>  (from 明鏡国語辞典)

The も softens the statement. 「そんなこと **も** ない」 sounds softer and less
decisive/assertive than 「そんなこと **は** ない」.

* 明鏡国語辞典 categorizes 係助詞(binding particles) as 副助詞(adverbial particles).




The も is used in the sense of...

> も 〘副助〙*  
>  ⓬ さりげなく取り立てて、文意をやわらげる。...  
>  ㋐《多く、文末表現に使って》一歩引く気持ちで、その判断をやわらげる。...  
>  「その件なら知らなく **も** ない」「そんな感じがしないで **も** ない」  
>  (from 明鏡国語辞典)

The も softens the statement. 「そんなこと **も** ない」 sounds softer and less
decisive/assertive than 「そんなこと **は** ない」.

* 明鏡国語辞典 categorizes 係助詞(binding particles) as 副助詞(adverbial particles).

