I understand his comment, but leaven is a negative word in spiritual hermeneutics.
I’m not Catholic or KC, but I know several KC well. I think they already do what was asked of them.
One type of leaven is baking powder, which is used to create biscuits and other quick breads, which are yummy but pale in quality to the other type of leavened bread, yeast breads.
Making bread with yeast is time consuming. The dough must be allowed to rise and is punched down, the allowed to rise again and the process is repeated, perhaps several times. Patience with working the dough produces good quality bread.
Which type of evangelization, liturgies, theology, etc. would you associate with each type of leaven?
Maybe we should “leaven” the military chapel Obama locked up and help support priests say mass? Be nice for a color corps to show up.