I agree, there is a time for purposeful sarcasm.

To me, it requires two conditions:

1. A person has already expressed their real perspective to a specific ‘opponent’, and

2. That specific opponent cannot see the hole in their own logic.

This Norm MacDonald radio clip is a good example.

He explains his true perspective, and only switches to sarcasm for one sentence (at 5:25), to show the opponent how she is being goofy [and it works].

His foundation of sincerity gives context to the sarcasm.

Conversely - nowadays - a common ‘communication style’ is to just spray aimless sarcasm at distant or imaginary foes,

which (to me) reflects a deeper cultural issue…

a hiding behind mockery, a suppression of real constructive bravery,

just dunking on one-dimensional charicatures of strangers (who might not actually exist).

[So I agree with you - there are times for purposeful sarcasm.]