People will try to convince you that some activities are bad. I'm thinking about drugs, casual sex, television watching and so on.
What I'd like to say is that bad can only be judged in context, so it's more meaningful to say that some activities block your time from being used on better things.
That three hours of TV wasn't bad... but you could have been that much better at playing guitar. Could've started a business or social group. Could've helped ANUS make more people aware of good metal. Could've socialized or read a book, or built a shed, or crucified a Nazarene.
It's not "bad," it's a waste of time.