Personally, I oppose the left's tendency to toy too much with language. I believe that habit stunts our analyses and makes us look like shysters to outsiders. Metaphors either work or don't work, to varying degrees. I'd put this one from Lorde way on the "doesn't work" end of the scale, for the reasons I've stated.
Meanwhile, I didn't say the whole phrase is simply wrong. I said its relationship to slavery (the language and reality of which are the material from which the metaphor tries to get its power) is simply wrong. Almost by definition, slaves must use the master's tools to attack the master. They have nothing else available. And, now that you mention it, the metaphor is also _doubly_ simply wrong as it relates back to slavery. Reading and writing were the master's tools. Acquisition and use of these was strictly suppressed by masters, as we all know.
Lorde's metaphor simply sucks. It throws out the baby with the bathwater. It deserves to be buried and forgotten.