Why saying 'no' to life is unacceptable

Just what counts as acceptable or unacceptable is obviously a cultural, social and historical variable. That being so, it might still be possible to make claims regarding broader structures of unacceptability, and certain motifs that, within epochs, dominate cultural production. We can perhaps begin by asking — today — just what might count as unacceptable in general. That is to say, one can imagine all forms of socially refused content, ranging from prohibited actions and lifestyles to censored content. But on what grounds or by what logic is the border between the acceptable and unacceptable drawn?