Inviting is one thing, praying with them and giving legitimacy to their religion is another. And when there has been no clear indications that he believes there is an absolute requirement for any non-Catholic to convert to Catholicism his invitations appear as empty gestures. He’s (and we are) better off not inviting in the first place.
Preach the Gospel daily, use words if necessary.
Trying to bring a person to a new way of thinking often requires several iterations of questioning. If this group of non-Catholics thought the Pope had horns and a tail, then the meeting would have demonstrated their preconceived notions were wrong. They would then be more willing to challenge other notions.
Not every conversion happens on the road to Damascus.