Why such lack of respect for the non-Catholic and the guests?

The Catholic Answers

The law is not prompted by lack of respect for the non-Catholic party or for the guests. It is prompted by respect for religious rites and for the worship of God. The non-Catholic has no more right to intimate Catholic religious practices than an unnaturalized citizen to all the civic rights of true subjects. The non-Catholic party may be as good as gold. But that is not the point. The point is that she is not a Catholic, and the Church is quite within her rights in saying how far she will admit non-Catholics to a participation in her privileges, even as a club is within its rights in saying how far non-members may participate in its privileges. But such restrictions as regards non-members cannot be construed as an insult. The Catholic Church is not bound to manifest equal approval of Catholic marriages and of mixed marriages alike.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty