It's only a joke.
ただの冗談だ
It's only right that he (should) know the fact.
彼がその事実を知っていて当然だ
It's only right [fair].
どう見ても正しい［公平だ］
It's only so much rubbish.
それはまったくのがらくたに過ぎない
It's only spitting (with rain).
（雨が）ぱらついているだけだ
It's out of the question.
そんなの話にもならない
It's outside my field.
それは専門外だ
It's partially my fault.
それはある程度私の責任だ
It's past a joke now.
冗談を超えている
It's peculiar that ....
…とは奇妙だ
