I dont understand. Arthur is an adult. It was consensual and it was outside club business. It wasn’t public either. Where is the scandal? Is he suppose to be PG for the rest of his career even in private?
My attempt to explain: catholic church has successfully used sexuality as a curse, and established "guilt + sex. pleasure" over many 100s of years in Europe. Spain might be no exception for that. That is still deep in the subconsious of the society engraved. pleasure-restritive and prudish.
Plus another effect, lets assume an alternative shituations to analyze further our problem:
A) Arthur breaking his leg while playing with children football.
scandal? - probably not
B) Arthur breaking his leg while playing with hookers
scandal? - probably not so much - just a slippery aspect of his carreer
C) Arthur STD with hookers?
scandal? - hell yea, now everyone else can point at him, and there is nothing more satisfying for masses than see stars falling, as this eases the pain of their own personel shortcomings. See he is also .... a little idiot /unfortunate / hit by bad luck/ ..... like me. It is the comparison where humans see semselves. There was once a study that found out people are happier if they earn 2000$ in an area where everyone else earns 1500$ than a district where they earn 3000$, due to better job, but everyone else earns 4000$. My self-picture is generated by reflections of other humans. (holds true unless you are Zlatan)