Greetings, John ---
Thank you for taking the time to write and ask your question.
I can say, without hesitation, Freemasonry has NO problem with Catholics, or any other religion. Though requirements for membership do vary slightly from state to state, for the most part men who are 18 (or 21 in some states), who have a belief in a Supreme Being, and are of good moral character are welcome to apply for membership in the Fraternity.
I was raised Roman Catholic. I became Protestant after my wife and I got engaged and wanted to attend church together. I have found NOTHING in the lessons of Masonry that conflict with the moral teachings of the Catholic Church. The issue is one that the Catholic Church has with Masonry.
Perhaps, this will an overly simple explanation, but, as I understand it, the Church has a problem with Freemasonry viewing all religions as acceptable, and the Catholic Church teaches the only true religion is the Catholic interpretation of the teachings of Christ.
A good friend of mine, who is a long time and distinguished Mason in my area was the President of a local St. Vincent DePaul Society, was a Treasurer for the Archdioses of Boston and was a very active member of his Roman Catholic church. The church has since asked him to choose between the Church and Freemasonry. He’s still a Mason and is now a member of another Denomination...this was a very difficult choice for him, but one that was driven by the Catholic Church, not Freemasonry.
I hope this answers your question and I also hope others will post their take on this very common question.
Again, thanks for taking the time.