Although it is a generally good practice to do no harm, there is no universal imperative to do so. This doesn’t mean everyone needs to be hostile to everyone, but nature tells us that violence is a very significant part of reality. We may not wish to do harm, however humankind follows no unified ideology and the evidence explicitly shows that humans harm each other every moment of the day. The Epicurean has to be ready for anything to preserve the individual’s freedom and pursuit of pleasure…and that may mean a show of force or even as a last resort a violent interaction.
Violence does not bring about pleasure, but is necessary to preserve the ability to continue experiencing pleasure. As with everything prudent judgement is critical. Being too heavy handed with an adversary may backfire on you and cause you to have ill repute or likewise being too passive will cause other adversaries to perceive weakness. So it becomes a perpetual cycle of maintaining vigilance and evaluating risks.