One of the reasons Catholic Church is opposed to freemasonry because the Catholic Church is the authority established by Jesus Christ, and it alone is authorized by God to administer oaths on matters of faith and morals.
To the extent that the freemasons administer oaths on matters of faith and morals, they have presumed to have authority which was not granted to them by God, but was granted to the Holy Catholic Church. I'm not talking oaths which only swear by God's name such as an oath one would take in a court of law - that has to do with matters of civil and crimminal law and not faith and morals. The court system is the legitimate authority on matters of crimminal and civil law. I'm talking about oaths which pertain directly to matters of faith and morals.
Anyone can say anthing they want about freemasons, and claim that it is or is not accpetable for a Catholic to also be a freemason, but if freemasonry presumes to administer oaths on matters of faith and morals, they have set themselves up an authority parallel to God's authority, are therefor out of bounds, and Catholics must avoid membership.
**No one can serve two masters. He will either hate one and love the other, or be devoted to one and despise the other. *(Matthew 6:24)*
When faced with an institution or organization which asks people to swear oaths, one must ask themselves what the oath pertains to. Criminal law? Faith and morals? Fraternal fellowship? Service to man? If the oath pertains to matters of faith and morals, then one must ask themselves who they believe the legitimate authority on matters of faith and morals on earth really is. If the organization asking people to swear oaths on matters of faith and morals is not the Catholic Church, then you have a choice to make about which authority you are willing to submit to.