flippancy

她对严肃问题的轻率态度让讨论变得毫无意义。

Her ___flippancy about serious topics made the discussion pointless.

他对这个严肃问题的轻率态度让在场的每个人都感到不适。

His ___flippancy about the serious issue made everyone in the room uncomfortable.

在严肃的法庭上，律师的轻率态度激怒了法官。

The judge was angered by the lawyer's ___flippancy during the serious court proceeding.