How do RC Christians remain so: RC that is,when the the history of their church is written in the blood of those it martyred?

Their eyes are so blind they cannot see.

The history of mankind is written in blood. Get over it.

The Catholic Church is the ONLY Church founded by Christ. Neither the gates of hell nor your filthy lies will overcome it.

Scriptures clearly says in Revelation 18:24 - that in Rome - Mystery Babylon - In her was found the blood of prophets and of God's holy people, of all who have been slaughtered on the earth." Rome can be identified as the mystery babylon from Daniel 9:26- which says people of the "prince"(beast/antichrist) who will come (in the future) will destroy the City and the sanctuary- Jerusalem destroyed by Romans in AD70. Thus people of the prince to come/antichrist are Romans. Rome is also the city with 7 hills and 7 rulers - Roman Ceasers (Revelation 17: 9-11) at the time of writing of Revelation by Apostle John which is about AD 54-68, when Nero ruled the Roman empire. From this we also know that Nero is probably the antichrist/beast as his numerology is 666 as the beast - Revelation 13:18.

Why? Apart from radical feminist lies in 20th century and idolatrous corruption of God's church by practice of intercession/veneration of saints (from 5th century onwards) and the many lies that are used to defend that idolatry, that caused much destruction in western society , Vatican- Rome -created Islamic lie for its power consolidation in middle east through Warraqah- Kadijah axis. Thus all these people killed by Islam through terrorism in the last 1400 years of its existense is done by Rome - Vatican.

Again Rome - Vatican Jesuits planted the Evolution lie through Darwin's grandfather Erasmus Darwin an active freemason controlled by Catholic Jesuits. Evolution lie has made the societies collapse by causing people to be deceived by idolatry and homosexuality (Romans 1:18-32).

Again Jesuits planted communist lie through freemason Friedrich Engels who controlled Karl Marx. Socialist Communist lie was initially promoted by Vatican with the aim of complete extermination of Jews whom catholics even today consider an obstacle for their global power consolidation just like their muslim slaves. Result was massacre of 6 million Jews by National Socialist Hitler and 25 million slavic people ( 20 million by the Jesuit Stalin and 5 million by the catholic Hitler). Add to this countless other innocent people killed around the world such as by communist dictators in Cambodia, China , Cuba etc.

If you donot want to come under the wrath of God almighty stop lying that God almighty and those who trust in him are the cause of lies like radical feminism , instead of exposing the real culprits which is Roman Catholic- Vatican- Mystery Babylon -Rome - that Capital of Satan and Fallen Angels from which Antichrist/Beast Nero will be resurrected for eternal wrath of God in the future.

So repent now all those who read this and leave the idolatry and lies and trust in God almighty who created and sustains you everyday, by accepting the eternal precious sinless blood of Lord Jesus Christ shed for the remission of sins of all mankind on the cross at Calvary, Jerusalem some 2000 years ago, so that all who will accept this salvation plan of God shall have eternal life.

The history of the CC is checkered. There are white squares too. Do you ignore these? Name me a church that is perfect.

For the same reason "biblical Christians" remain so, even though the bible describes a story written in the blood of countless people.

That reason is that most of them think things are different today.

The 2,000 year history of the one Church Jesus Christ founded is written in the pages of the Bible, and the promises of its founder - "The Holy Spirit will guide you into all truth", and "Whatsoever you bind upon Earth is bound in Heaven", and "He who hears you hears Me".
The history of those who have defected from His Church is written in the doctrinal chaos of Protestantism - over 6,000 unauthorized conflicting manmade denominations, each claiming to be teaching from "the Bible alone", yet the teaching of each one contradicting the teaching of the others. And that doesn't even include the 20,000+ so-called "non-denominational" Protestant churches! Truth cannot contradict truth, so untruth is obviously rampant in the teaching of such churches. Which you would expect in a system that exists in direct opposition to the plainly stated will of Jesus Christ concerning His followers - "That they all may be ONE, even as I and My heavenly Father are ONE".

Catholicism is the One True Faith and a person can know this with certainty by reciting the rosary each day with care.