I don't think anything about pain as a concept or feedback process is bad. The things which may cause or accompany pain however are bad or challenging and can cause harm to sustainable life. That is what people actually don't like. I am unfamiliar with cases where pain does not accompany some destructive situation.

On the flip side, I like the pain in my muscles after exercise because I understand it's origins and it is signaling to me that I successfully broke muscle down which I have a reasonable expectation of growing back stronger.

Pain in and of itself is the most effective signal for motivation that can occur in the animal kingdom. What we refer to as pain is simply a feedback mechanism for indications of change in homeostasis.

I wrote this blog post a while back on brain pain and how I think it is similar to muscle pain, which I think is apropos.