For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
'Who is the liar? He (she) who denies the Father and the Son'. i.e.. Cults usually deny the Trinity.
To me there is a difference between a sect and a denomination. Catholic is a sect, Protestant is a sect. In the Bible there was a sect called Pharisees who, like the catholic leaders, must have a tangible relationship with God and man (Matthew 23:5). Catholics use items to supplement their relationship with God as the Jews did. On vaticanva.com there are examples of the Pope being worshipped as Lord in the physical.
Protestant has many denominations. (I agree that JW’s and Mormons are cults.) But if anyone accepts Jesus as Lord and savior to me they are not against Him they are for Him. (Mark 9:40) in 3 John 9-10 we have a believer who has adopted his own way to believe, this is sectarianism. Sectarianism is forbidden in the body of Christ (1st Corinthians 1:10) Not all catholics believe that the Pope’s words are equal to God, even the Vicar literature says the pope is leader and not Christ. I’ve meet some who don’t do Hail Marys. Maybe they rebelled.
There’s also non-denominational believers who don’t want to esteem any part of the Bible higher than the other, not that other denominations do. It’s just some denominations will praise God more in one aspect than another. In Acts 18 and 19 the believers mentioned needed to be taught the word more accurately. And some won’t use certain gifts, such as speaking or interpreting tongues. I believe there is a different denomination for every person. I can’t see two people believing alike, since it is the living word and everyone lives different. My denomination I call Second Adamite, lol (1st Corinthians 15:47).