I've gone over this plenty of times, so I'm sure that if you're a regular reader, you know the drill by now. However, regardless of who you are, I've come up with another way to phrase "Suffering is bad" so that it sounds more empirically testable. Here it is:
Those who suffer do not want to suffer.
If we can verify this statement empirically, then that's all that we need to do; there is no more to "prove." You can't want to suffer; as soon as you come to enjoy something, it's no longer causing you to suffer.