Why do so many Christians act like jerks?

Scripture
Galatians 2:11-16
‘But when Cephas came to Antioch, I opposed him to his face, because he stood condemned. For before certain men came from James, he was eating with the Gentiles; but when they came he drew back and separated himself, fearing the circumcision party. And the rest of the Jews acted hypocritically along with him, so that even Barnabas was led astray by their hypocrisy. But when I saw that their conduct was not in step with the truth of the gospel, I said to Cephas before them all, “If you, though a Jew, live like a Gentile and not like a Jew, how can you force the Gentiles to live like Jews?” We ourselves are Jews by birth and not Gentile sinners; yet we know that a person is not justified by works of the law but through faith in Jesus Christ, so we also have believed in Christ Jesus, in order to be justified by faith in Christ and not by works of the law, because by works of the law no one will be justified. ‘
 
Galatians 6:1-2
‘Brothers and sisters, if anyone is caught in any transgression, you who are spiritual should restore him in a spirit of gentleness. Keep watch on yourself, lest you too be tempted. Bear one another’s burdens, and so fulfill the law of Christ. ‘
 
Quotes and References
“Religious faith as evidenced by ordinary followers is the single strongest proof that there is no god.” – Christopher Hitchens
 
“Therefore, those who have sponsored the modern dichotomy of reason and meaning have not been able to live with it. Jean-Paul Sartre quarreled with Camus because he felt Camus was not being consistent with to their basic presuppositions. This was true, but then neither was Sartre consistent when he signed the Algerian Manifesto…. He took up a deliberately moral attitude and said it was an unjust and dirty war.” – Francis Schaeffer (The God Who is There)
 
“The message about talking about Mormons with love seems hollow. Especially when I’ve heard them joking about us. It would be like explaining you’ll feed the starving in Ethiopia but then laugh about how scrawny they are… I don’t find either very funny.” – David Kinnaman (UnChristian)