And excommunicating the Le Pens (after the election of course) or better yet backing up the local bishops in France doing it would be a similar move on the right side of history.  As would have Pius XI or Pius XII excommunicating Mussolini and Hitler.  It is a tool that the Catholic Church has to deal with people who are spreading hate and who are actually harming the world through their extremist hatred.  I think the far right populists are that scary and evil and need to be dealt with more harshly than the Church just ignoring them.