He calls for no action on the part of the wronged. Rather, he implies a course of action for those who bear the guilt. In response to the publication of Tomas' letter, the Russians invaded Czechoslovakia in the summer of 1968, effectively putting an end to the liberal reforms of the Prague Spring. In the novel, at least, Tomas' ingenious formulation causes an extremely ill side effect - Russian tanks in the streets of Prague. No surprise here.
History is a joke.
What's particularly interesting about this scenario, however, is how Kundera deals with the question of guilt. Mistrust all in whom the urge to punish is powerful. Verily, their souls lack more than honey. They have turned their backs on life, but Tomas is not one of them. He does not seek revenge.