Are all Christians hypocrites? Why is the claim that Christians are hypocrites so popular? Is it true?

TL;DR:

Christians are called hypocrites for many reasons. However, Christians who recognize their sin are not hypocrites but rather, sinners in need of grace just like everyone else.

Hypocrites are people who say one thing and then do the exact opposite—people whose preaching does not match up with the pattern of their lives. Christians often get a reputation for being hypocrites. Some of the time, these accusations are fair and true. Other times, they aren't. When Christians are judgmental and forget that they also are sinful human beings, they are hypocrites. When Christians say one thing and do another, they are hypocritical. While Christians will all fail at some point, not all Christians are hypocrites. Many Christians are keenly aware of their own sin and failures and do not judge others or require Christian morality from those who have not decided to follow Christ. Despite our sin, all Christians are called to uphold goodness and beauty and to speak the truth—this does not make us hypocrites. Humbly admitting our sin and recognizing our need for God reveals that we are not hypocrites but rather, sinners in need of grace.

from the old testament

Isaiah 29:13 addresses the hypocrisy of worship, where people outwardly honor God with their words but fail to live with true reverence or love for Him. Ritualistic or lip-service worship with hearts far from God is condemned.
In Amos 5:21–24, God says He hates empty religious rituals. God calls offering sacrifices or observing religious holidays while neglecting God’s justice and righteousness hypocrisy.
“With what shall I come before the Lord, and bow myself before God on high? Shall I come before him with burnt offerings, with calves a year old? Will the LORD be pleased with thousands of rams...?” (Micah 6:6–8). God rejects mere outward sacrifices if the worshiper's heart is not in the right place and calls for justice, mercy, and humility, rather than ritualistic offerings.

from the new testament

Paul confronted being hypocritical by saying, "Therefore you have no excuse, O man, every one of you who judges. For in passing judgment on another you condemn yourself, because you, the judge, practice the very same things" (Romans 2:1).
Paul also said, "Who are you to pass judgment on the servant of another? It is before his own master that he stands or falls. And he will be upheld, for the Lord is able to make him stand" (Romans 14:4).

implications for today

Christians are called to humbly live their lives in Christ, communicating a passion and interest in what they believe, and they sometimes fail to live up to their own standards. Other Christians judge harshly or use morality and standards to control people or control the way people see them. It is important to know the difference between these two types of Christians because only the former is exhibiting Christian behavior. The latter may also be truly connected to Christ and simply showing immaturity or making a mistake (Galatians 2:13). But Christians are not supposed to be hypocrites, and when they are, it is a sign something has gone wrong.

understand

Not all Christians are hypocrites.
Christians who judge others without recognizing their sins, or those who do not practice what they preach, are hypocrites.
Christians will sin, but that does not make them hypocritical.

reflect

Have you ever been accused of hypocrisy? What were you accused of, and how did you handle it?
How do you distinguish between struggling with sin and pretending to be someone you're not?
How can we ensure our actions match our beliefs, despite our imperfections?

engage

Why do people confuse sin with hypocrisy, and how can we clarify this?
How can Christians uphold moral standards without being hypocritical?
How can we support each other in avoiding hypocrisy, both by judgment and by not living up to God’s standards that we say we uphold?