Those studies simply assume that everyone, and every group, that associates itself with Christ is really Christian, there is no standard whatsoever. But Jesus laid down a standard! The real question here is, what is a Christian? And what is authentic Christianity? IMHO opinion much of Christianity now and in history, isn’t what Jesus would recognize as what he died for. But inauthentic Christianity is talked about even in the New Testament.
"“Not everyone who says to me, ‘Lord, Lord,’ will enter the kingdom of heaven, but only the one who does the will of my Father who is in heaven. Many will say to me on that day, ‘Lord, Lord, did we not prophesy in your name and in your name drive out demons and in your name perform many miracles?’ Then I will tell them plainly, ‘I never knew you. Away from me, you evildoers!’" (Matthew 7:21-3)
"For false messiahs and false prophets will appear and perform great signs and wonders to deceive, if possible, even the elect." (Matthew 24:24)
"For the time will come when people will not put up with sound doctrine. Instead, to suit their own desires, they will gather around them a great number of teachers to say what their itching ears want to hear. They will turn their ears away from the truth and turn aside to myths." (2 Timothy 4:3-4)
"The Spirit clearly says that in later times some will abandon the faith and follow deceiving spirits and things taught by demons. Such teachings come through hypocritical liars, whose consciences have been seared as with a hot iron. They forbid people to marry and order them to abstain from certain foods, which God created to be received with thanksgiving by those who believe and who know the truth."(1 Timothy 4:1-3)
Using my own church as an example, since it’s what I know, every single person that has been baptized is a, “better person” than they were before the conversion, according to anyone’s standard. And that’s not saying we’re all perfect and don’t sin and slip up. So those studies don’t say anything to me, since they don’t hold any person or group to the standard of Christ.
And of course I never said that we’re not called to, “oppose injustice and oppression”. But only our purpose is a spiritual one, just like our Lord’s was, and those born again will serve the poor and needy and will do good works. But that’s completely different than claiming that we’re called to go out into the word to, “end oppression and injustice”. Jesus never called us to do that, and neither did anyone else in the NT.