One of the important things in Islam is to be peaceful, especially when behaving and talking to people. God says to the Prophet Muhammad:
It was by the mercy of Allah that thou wast lenient with them (O Muhammad), for if thou hadst been stern and fierce of heart they would have dispersed from round about thee. So pardon them and ask forgiveness for them and consult with them upon the conduct of affairs. And when thou art resolved, then put thy trust in Allah. Lo! Allah loveth those who put their trust (in Him). (159) Al Imran 3:159
This is a lesson of behaving with people from the God.
Clean Tongue
In the last decades, many people in Western cultures started talking *unclean*. They say bad words when meaning to use them or not. Even on the Internet, they use them and sometimes they replace them with a group of asterisks. In the Middle East, especially Muslim countries, it is a taboo to swear or curse people, animals, fate, ... etc. In a Muslim community, one who says bad words is considered undisciplined by his/her parents and his/her manners are questioned. Islam calls for decency in cloth, behavior, and talk. Refraining from uttering bad words is rewarded.
On the authority of Abu Dhar Jundub bin Junadah, and Muadh bin Jabal that the messenger of Allah said:
"Fear Allah wherever you are, and follow up a bad deed with a good one and it will wipe it out, and behave well towards people." Source: Islam World
On the authority of Ibn Abbas that the messenger of Allah, among the sayings he relates from his Lord is:
"Allah has written down the good deeds and the bad ones." Then he explained it [by saying that] : "He who has intended a good deed and has not done it, Allah writes it down with Himself as a full good deed, but if he has intended it and has done it, Allah writes it down with Himself as from ten good deeds to seven hundred times, or many times over. But if he has intended a bad deed and has not done it, Allah writes it down with Himself as a full good deed, but if he has intended it and has done it, Allah writes it down as one bad deed." Source: Islam World
A group of the Jews came to Allah's Messenger (may peace be upon him) and sought his audience and said: Al-Samu 'Alaikum. 'A'ishah said in response: Al-Samu 'Alaikum (death be upon you) and curse also, whereupon Allah's Messenger (may peace be upon him) said: 'A'ishah, verily Allah loves gentleness in every matter. She said: Did you hear what they said? Thereupon he said: Did you not hear that I said (to them): Wa 'Alaikum (and the same to you). Source: al-islam
Allah's Messenger (may peace be upon him) said: Allah is self-respecting and a believer is also self-respecting. The respect of Allah is injured if a believer does what He has forbidden him to do. Source: al-islam
The Prophet (may peace and blessings be upon him) observed: None among you will be a truthful believer till he likes for his brother or for his neighbor that which he loves for himself. Source: al-islam
When a believer faces a difficulty, s/he should be patient and do not curse his/her life or fate.
I heard Allah's Messenger (may peace be upon him) as saying: whenever a believer is stricken with discomfort, hardship or illness, grief or even with mental worry, Allah shall expiate some of his sins. Source: al-islam
Ibn Mas`ud (May Allah be pleased with him) reported:
The Messenger of Allah (PBUH) said, "A true believer is not involved in taunting, or frequently cursing (others) or in indecency or abusing.'' Source: Witness-Pioneer
Abud-Darda' (May Allah be pleased with him) said:
The Messenger of Allah (PBUH) said, "When a person curses somebody or something, the curse goes up to heaven and the gates of heaven get closed. Then it comes down to the earth and its gates get closed. Then it turns right and left, and if it does not find an entrance to go anywhere, it returns to the person or thing that was cursed; if he or it deserves to be cursed; otherwise it returns to the person who uttered it.'' Source: Witness-Pioneer
Muslims must behaving as great as the Prophet Muhammad, Peace Be Upon Him, was. God says about Muhammad:
And lo! thou art of a tremendous nature. The Pen 68:4
In the end...
It is really nice to be great than the rest. Try always to keep your tongue and behavior pure and clean :)