Because they know Roman Catholicism was regarded as a means of supporting Spanish colonialism. I don't think Spain could occupy the Philippines without the propagation of Catholicism for 333 years. You can find many historic facts that a religion was used as a main means for colonialism. As an example of it, many Caucasian Christian people slaughtered lots of native American people in the name of the development and the propagation of Christianity for 400 years since Columbus got to America in 1492. And finally they gained control of America where is more than four times wider than the European continent.