Because he wears a cassock!

No, not really, but wearing it does signify something.

Fr. Michel-Marie, a Cassock in Deep Marseille by Sandro Magister
The life, works, and miracles of a priest in a city of France. Who has made the faith blossom again where it had withered

As a young man he sang in the nightclubs in Paris, but then over the years there emerged the vocation to the priesthood he had had since his childhood. His guides were Fr. Joseph-Marie Perrin, who was Simone Weil's spiritual director, and Fr. Marie-Dominique Philippe, founder of the congregation of Saint John. He studied in Rome at the Angelicum, the theological faculty of the Dominicans. He was ordained a priest in 2004 by Cardinal Bernard Panafieu, the archbishop of Marseille at the time. He writes books, the latest of which is entitled "Au diable la tiédeur," to the devil with lukewarmness, and is dedicated to priests. He is pastor at Saint-Vincent-de-Paul.

From the article by Marina Corradi:

Why the cassock? "For me" – he smiles – "It is a work uniform. It is intended to be a sign for those who meet me, and above all for those who do not believe. In this way I am recognizable as a priest, always. In this way on the streets I take advantage of every opportunity to make friends. Father, someone asks me, where is the post office? Come on, I'll go with you, I reply, and meanwhile we talk, and I discover that the children of that man are not baptized. Bring them to me, I say in the end; and I often baptize them later. I seek in every way to show with my face a good humanity. Just the other day" – he laughs – "in a cafe an old man asked me which horses he should bet on. I gave him the horses. I asked the Blessed Mother for forgiveness: but you know, I said to her, it is to befriend this man. As a priest who was one of my teachers used to tell those who asked him how to convert the Marxists: 'One has to become their friend,' he would reply."