Why is it that some born again Christians utter blasphemous words and think nothing of it ? Why is it that they write blasphemities and think nothing of it ? Again, why is it that some born again Christians read blasphemities and it has no effect on them ?  it could be due to a number of things; due to a lack of knowledge of their spoken tongue about when to use certain words and when not to use them; due to a lack of shepherding and fellowship; due to giving in to Satan during certain conversations. Most of the times that these blasphemies occur is during an argument or an overwhelming experience when the person is lost for words and utters an interjection (to exclaim in interruption.) 

The following letter is not to condemn or to force an open confession but, as the Title suggests, Exort. Personally speaking, it really hurts me, pierces my heart when I'm in company with someone who swears or blasphemes and when I'm reading notes posted by other Brothers and Sisters. 

Almighty God, to the intent of his most holy name should be had in honour and evermore be magnified of the people, commands that no man should take his name vainly in his mouth, threatening punishment unto him that unreverently abuses it by swearing, forswearing and blasphemy. To the intent therefore that this commandment may be better known and kept; it shall be declared unto you both how it is lawful for Christian people to swear and also what peril and danger it is vainly to swear or to be forsworn.

The Commandment. Exodus 20, v.7.

Thou shalt not take the name of the Lord thy God in vain: for the Lord wilt not hold him guiltless who taketh His name in vain.