Maybe it's more like walking into the room, seeing three square meters of blood, then saying "holy fucking shit something is wrong"

Your misunderstanding is that people think the blood on the floor is the problem.

And you're right: sometimes there is a perfectly good reason why the floor is covered in blood.

This reaction wants to redefine adulthood as post 25

It's even more than that, it wants to make adulthood some kind of sliding window where the age of the older partner defines how "adult" and "capable of making decisions" we see the younger partner, and the older a person gets the more people at the lower end of the age range get excluded for them from this fictional adulthood. For example: 60 and 30 would also be seen as inappropriate.

Now it's perfectly normal for younger people not to find much older people attractive or suitable to have a relationship with and vice versa, and they may even find the idea repulsive, but this is still a personal preference. It's probably even the preference of the majority of people, but that does not mean we should take away the agency of adults to choose their partners when they have a different, non-conforming preference. At that point it has nothing to do anymore with protecting vulnerable people from predators, but about imposing your own preferences and dating standards on other people, and you're quite right in calling it out for the neo-puritanical and conservative thinking that it is.

dis guy arguments.

It's interesting, I agree with what you say here and this is what I thought you were saying... But when I read it the first time without additional context it kind of sounded like the argument was that we are infantilizing the older individuals. It appeared that the argument could have been: we make the "rules" and apply them to the older half because they are the ones who are incapable of dealing with their emotions, needs and desires.

You are right that it is in the subtext. This is the same poor argument that men are unable to control their desires if a woman wears revealing clothing... Just restructured around women being "taken advantage of" by a "smarter more mature male".

It might also have been why the other commenter thought you were defending the conservative position. There are two steps here that you made when the intermediate step could also apply and would be an honestly revolting position to defend. I couldn't quite figure out if it was a reasonable position or a very well hidden dog whistle.