I'm not sure I can really make an appropriate generalisation of the broad attitude towards it. I can, however, cherry pick Diane Abbot's views because she's often called upon for soundbites and political debates. As a consequence, my comment is a subset of reality.
In this case the fears stem from the perception that children viewing porn and sexualised content is damaging. In Diane Abbot's case [1] the concern is that sexualised environments might construct inaccurate attitudes towards women/sex in children.
I suppose that falls in the first and final scenarios you gave.