Being better at violence doesn't make you more left, it makes you better at violence. That can be useful, but it isn't the same thing. Your argument boils down to "might makes right" and could be expanded to classify social democracy as "more left" (after all, it's left of the global status quo and its citizens are the happiest on average). In fact, you might even be able to use the argument for liberalism; it's left of monarchy and fascism. Sure, it frequently decays into fascism, but so did the USSR.