First of all, it's a reminder not to take oneself too seriously, especially in out-sized situations involving direct confrontation with power. Laughter, in such settings, teaches humility, restores one's sense of proportion. You can only make peace with joy. Rare is the activist who is not to some degree angry. The activist whose larger goal is to fix the world laughs.
Laughter is the pathway to redemption.
Folk-singing Rabbi Shlomo Carlebach approached laughter differently. For him, laughter meant accepting whatever God doles out. The cat soiled the coat and the housekeeping staff threw it out. Told he had lost his coat, the rabbi laughed. Never mind that in its pockets were his money, his passport, his plane tickets, his schedule.