Don't use this as a pretext — let's stick to what's in front of us.
Tips
history
Wu Jianren's late-Qing novel 《痛史》 has a scholar say: "I get worked up and scold them — this is what you literary folks call 借题发挥." The phrase describes the writer's trick of using any topic as a launchpad for unrelated arguments.
usage
Usually slightly negative — implies the person is opportunistic or petty, using a minor trigger to vent larger grievances.
