Even in context, it's still a stupid metaphor, at several levels. As it applies to capitalism, "the master's tools" is a much wider set of things than just propaganda about race and gender and class. As it applies to slavery, the metaphor is simply wrong. The master's tools are the best and only way of leveling his house. It's a failed attempt at poetic rabble-rousing. This gun shoots backwards. The master's lies hold us down, but he's got some tools and a house that we want to take over and turn toward better purposes.