The left has become no better than the townspeople in the scarlet letter.
First, would a leftist or a conservative be more likely to make fun of victims of Islamist violence? I would say a leftist.
Second, would a conservative or a leftist be more angered by someone who made light of an attack on Americans by Muslim terrorists? I would say a conservative would be the obvious answer.
Third, surely you realize that The Scarlet Letter was written by a leftist in order to demonize conservatism, yes? That the townspeople of the book are a leftist's caricature of his hated conservative neighbors?
Ultimately, if you are going to amuse yourself by mocking the still-raw wounds of others, you should probably expect that others will amuse themselves by mocking you and exposing your faults to the world.
Those who live by social media will die by it.