Not serious about a serious subject, in an attempt to be funny or to appear clever. (Cambridge Dictionary)
If you describe a person or what they say as flippant, you are criticising them because you think they are not taking something as seriously as they should. (Collins Dictionary)
Lacking proper respect or seriousness. (Merriam – Webster)
Brash and Flippant. Thesaurus. Plus.
‘Flippant’ and ‘foolish’: Joe Hockey called out for Kerala floods tweet.
Many on Twitter called him out for his tweet, labelling him ‘flippant’ and ‘foolish’ for linking heavy rains in India to Australia’s drought situation.