It does actually diminish it as it:
Commits to the naturalist fallacy
Makes the concession that somehow it's 'a moral evil for us, which we have identified' which leads into;
Acceptance of morality as ultimately subjective which then leads into;
Observable negative outcomes/harms are matters of opinion which then leads into;
That which is observed, and can have opinions formed of it, is subjective that ultimately distills further to;
Any aspect of society that comes from human thought is up for debate and/or is a product of culture.
The golden median fallacy is for children and objective morality exists. It does not mean that objective morality exists in equivalence, and it is a topic that requires nuance and genuine understanding making it unfit for handling by mentally malformed ideologues who take positions based on persuasion rather than correctness.
Rape is not a social construct, end of discussion.