A lot of what is called Christian morality today is not necessarily Christian, but more accurately described as Middle Class Christianity. It is the Christianity influenced by the Victorian era politeness and the rather quiet in door working spaces of many Christians, who tend heavily towards the middle class.
Here are examples of the difference:
Middle Class Christianity: Don't be harsh and use mean words to those who come to you, especially if they are in need.
Christianity: Jesus said to the Syrophoenician woman: You don't give the children’s food to the dogs (Matt 15:21-28, Mark 7:24-30).
Middle Class Christianity: It is wrong to even insult those who reject the message of Jesus.
Christianity: Jesus said to the disciples to shake the dust of their feet when leaving an unbelieving town or even home (Matt 10:14). A visible and very offensive gesture in his day. Use your imagination to think of similar offensive gestures
Middle Class Christianity: Quiet kindness and addressing your audience in calm smooth tones is the way to address people. Don’t use ad-hominins, stereotypes, or harsh language.
Christianity: Jesus in the gospel of Matthew: Woe to you Pharisees, you brood of vipers, you snakes, you white-washed tombs, you rotten corpses twice dead, you sons of hell (Matt 23).
Middle Class Christianity: Always use reason, dialectic and let your passion be bridled.
Christianity: Paul to the Judaizers: why don't you go and cut of your manhood’s (Gal. 5:12) you dogs (Phil. 3:2). Now that is powerful rhetoric. Indeed Paul was very good with rhetoric. Though yes, like all rational thinkers, he preferred dialectic, he still used rhetoric when it was useful.
Middle Class Christianity: Never, ever use bad words. Bad words are sin, bad words are never to pass your lips.
Christianity: Use bad words for bad things. For example: Paul refers to anything we would trust in for salvation other than Jesus as ‘skubala’ (Phil. 3:8). The Greek word 'skubala' is translated often as 'refuse' or 'rubbish' in English, but the KJV translated it 'dung', which is closer to its actual meaning. The word was actually the 1st century version of the word crap/B.S.. I am not making that up, everyone who has studied Greek knows this. Then there is Jesus using the word "Raca", a harsh and brutal insult (Matt. 5:22-23). Key point: they did not use these words to curse people. But the words themselves are just words, with a proper use in context.
Middle Class Christianity: Don't insult people.
Christianity: "The devil rides you", my favourite Martin Luther quote. Jesus, John the Baptist, Paul and John the apostle all insulted people. John the Baptist seemed to have a favourite: “You brood of vipers” (Matt. 3:7).
Middle Class Christianity: Is over-weighted with quiet middle class people who work in quiet controlled environments, where politeness and other such manners are part of the culture of the home and work environment.
Christianity: Is vibrant and open to many different people from various cultures, and is not just confined to the quiet submissive types who frequent office buildings, and knitting circles. Christianity is a religion that is for all people. Not just people who tend towards quiet and calm and polite conversation.
Now this post is not arguing that we should always use these harsher tones and harsher words, just that they are not always sin, if used properly, as Paul, Jesus and other Biblical people used them. This is not a summary of all of Christianity, there is much more to Christianity. But don't confuse actual Christianity, with Victorian niceties, and white, middle class culture.