"objectively obscene or extreme" - is there a clear definition for obscenity? I feel like there was a famous quote from a judge on the SCOTUS to effect of "I'll know it when I see it", but law is not an area that I have expertise in.
It’s evolved over time. The basis was content which was deemed to “deprave and corrupt those whose minds are open to such immoral influences". The next step was to remove protection status only for speech which is “patently offensive" and "utterly without redeeming social value".