It really is none of our business …his job is to rejuvenate France and show every one what a
great country it is.
He is the President not Brigitte and for a woman of mature years, she has aged very well, good luck to them both. I would love to know her beauty secrets.
If he is happy?? Why should we bother??
Agree with the comments above, plus in any case I suspect that technically it contravenes article 9 of the French Civil code
https://www.legifrance.gouv.fr/affichCodeArticle.do?cidTexte=LEGITEXT000006070721&idArticle=LEGIARTI000006419288
"Chacun a droit au respect de sa vie privée.
Les juges peuvent, sans préjudice de la réparation du dommage subi, prescrire toutes mesures, telles que séquestre, saisie et autres, propres à empêcher ou faire cesser une atteinte à l’intimité de la vie privée : ces mesures peuvent, s’il y a urgence, être ordonnées en référé."
It is wrong! It would only be not wrong if it were to be morally and politically acceptable to “raise an eyebrow” about how any couple got together. In fact, it is more than wrong it is disgusting that anyone should feel that he or she has the right to debate the private life of a couple.
To coin a great Anglo-Norman phrase, “Honi soit qui mal y pense.” Translatable as “If you think this weird, take a look in the mirror, weirdo…!” 
I agree entirely Mark. It seems even the Grauniad is not immune to the general prurience of the British press.
Charming personality surpasses beautiful look. Age gap doesn’t matter that much.