The problem of course is not annoying the underperformers, but you want to avoid annoying the valuable engineers who get things done and keep the company runnin

The problem of course is not annoying the underperformers, but you want to avoid annoying the valuable engineers who get things done and keep the company running. There's plenty of demand for engineers -- if they want, they could find another job in a week where they don't have to deal with hostile management. Treat people well. Assume the best and let them prove you right, rather than assuming the worst and making them prove you wrong.