I have been both reading and studying the Hebrew Bible and the New Testament for 68 years. I must apologize as I have not yet got to the part of the New Testament were Jesus and the Apostles (we only have Peter, James and John) are ever "defending truth." They were documenting the truth that Jesus was the Son of God who gave his life that all who put their faith in Him will not perish. The truth that Jesus ate and socialized with totally corrupt sinners. The truth is that even when Jesus's closest Apostle denied Him 3 times Jesus continued to love Him. Jesus never had to defend truth. He was truth and revealed truth thus no other "truth" required harshness. Jesus strongest condemnation was for those who practiced a super-pious form of religion but had no heart or love for God of His creation. Jesus called them a den of vipers because they had a "form" of religion but knew nothing of love, forgiveness, mercy and justice. Perhaps a warning for today as well. If our "religion" is loveless (except theoretically or intellectually) lacking any concept of real forgiveness, mercy or justice that we too are but a den of vipers.
There is a pretty extensive corpus of instruction, mostly by Paul about Jesus's call for his followers to live a moral, serving and loving life. Jesus "truth" is that a rich man will have little or no chance of getting to heaven unless God intervenes in his life to convert him into giving away his riches. Jesus's truth is that we must take up our cross daily. Jesus truth is that you must love God deeply and your neighbor as yourself and in the parable of the Good Samaritan makes it clear that your "neighbor" is anyone needing your loving help. Jesus truth is that you cannot love money and love God. John's truth is that if you say you love God but hate any kind of neighbor you are a liar. Paul's truth is that no matter how much faith you claim to have, if you don't have love, your faith claim is just noise to God. Matthew recounts Jesus description of the criterion by which each person will be judged in chapter 25. That is the Gospel truth that almost no modern Christian has ever heard in a sermon.
There are many who claim their sect's, denomination's, or church is the arbiter of what is "true." Thus we have 450,000 different denominations, quickly dropping memberships driven by the adoption of politics as a means of power, perversion and corruption within the "church" on a equal level to non-Christians, billionaire pastors, the "prosperity Gospel," and the invisibility of Christianity in any community or country. Nobody could pick out Christians from Pagans if they only looked at checkbooks, dress, entertainment, business ethics, morality, marital fidelity and families. What more harsh truth is there than what is happening in our world today of invisible Christianity.