I don't really want to get into this discussion, I think it's grim how you just go "ah 16, it's legal, so that's fine then" but I do want to point at that we have actually not made the decision to put the line at 16.
In most cases, 16 is the age of consent but...
If the older person is in a position of authority or responsibility it is 18. This is mainly aimed at positions like school teachers because we don't feel happy about them fucking 6th formers, or at scout leaders, or counsellors or whatever. In law it would be extremely difficult to define a celebrity but I'm pretty sure most of us would agree that celebrities exist in a position of power, authority and privilege over teenagers which would put them in the same moral area as teachers, social workers etc when it comes to relationships with 16-18 year olds, unless that celeb is themselves a teenager... which brand most definitely was not.
There is also the "quirk" of the UK legal system that whilst you can consent to sex at 16, you cannot consent to being filmed/photographed, that age is also set to 18, anyone under 18 being filmed/photographed is child abuse in the eyes of the law... because a 16 year old is still a child.
So "the line" is in fact somewhat blurred, and as I said at the start, it's grim that you want to make it some kind of hard divide between ok and not ok, and can't seemingly see why everyone else thinks it's fucking dodgy for a 30 year old to be dating a 16 year old.