Idiotly

[…], and in order to win the support of those who could not think for themselves, you deliberately and falsely represented yourself as the holder of several Doctor's degrees and idiotly claimed to be the Coming Master.

Source: wiktionary

He remembered their faces, red and idiotly merry with excited ridicule, so fiercely eager to lay indignity on someone else.

Source: wiktionary

Whimsic fantasy, grub fact, pure senseless music—none in itself would do; to embody all and rise above each, in a work neither longfaced nor idiotly grinning, but adventuresome, passionately humored, merry with the pain of insight, wise and smiling in the terror of life—that was my calm ambition.

Source: wiktionary