手て前まえ定じょう規ぎ

noun

self-serving logic; convenient reasoning

Refers to reasoning that is twisted to suit one's own interests or convenience, often used critically.

• 彼かれの言いい分ぶんは手て前まえ定じょう規ぎで、まったく説せっ得とく力りょくがない。

  His argument is self-serving and completely unconvincing.