As to Megan Kelly's comments on pedophilia, English law makes a clear distinction between sexual offences committed against children under 13, whom the law views as developmentally incapable of understanding or agreeing to sexual activity in any meaningful way, and those committed against children 13 or older but under 16, whom the law regards as capable of understanding sexual activity and as developing autonomy, at least to a degree, but nevertheless as needing protection because they lack the maturity meaningfully to consent.
Consequently, there are two separate sets of charges available to the prosecutor, depending on whether the child is under 13 or under 16. UK sexual offences law also prohibits sexual activity children under 18 in particular circumstances (the general age of consent is 16), where the adult is in a position of trust or authority, just as it protects in various ways and circumstances adults who, because of mental or developmental difficulties, are incapable of proper informed consent.
I don't see what's wrong with this. It seems to me to recognise the difference between developmental stages, and it works well enough in practice.
But neither do I see why this distinction is particularly important outside the legal context. Sexual activity with a child under 16 is still a very serious criminal offence. It's just somewhat less serious, when it comes to sentencing, than rape or sexual assault of a child under 13. It's not as if the fact the victim was 13 or older excuses the defendant in any way.
ETA: I think it may be that people on the right would rather think in terms of perverts vs normal decent people like us than in terms of people who respect the autonomy and consent of others and those who don't.