The Jansenists are the Catholics influenced by John Calvin, who stressed a rule oriented Christianity: including upright living, hard work and honesty.
The Jesuits were their enemy and finally got them supressed by the Pope, partly by pushing the Vision of St Margaret Mary of the Sacred Heart, which stresses God's mercy (as a doc, however, I suspect St Margaret was what we call a simple schizophrenic based on her non visionary behavior, and her visions rewritten to make them sound logical)
The Irish church, which had strong ties to France, was also influenced by Jansenism, and of course, the Catholic church in the US was essentially an Irish run church up to recent years.
Since the US culture is strongly influenced by Calvin, and the pious Catholics in the US influenced by Jansenism/Calvinism, you can see the reason behind lay Catholics in the USA opposing Francis’ idea of mercy, which goes overboard: Not just for repentant sinners but for non repentant manipulative sociopaths like the pedophile and financially greedy bishops.
Actually you need both mercy and a stress on clean living.
and one of the results of the Jesuits “winning” the fight in France was the French revolution: Because the church ignored the corruption of Catholics in the royalty and government, those wanting reform became not just anti royalty but anti Catholic.
I think the writer was trying to say was that these same rules oriented folks ended being viewed as “dour” folks, no joy minded folks.