An interesting thing happenned at work this week.
As a Christian there are things I, as a rule, don't say and certain things I won't say; blasphemy being one of the latter. Colossians 3:5-8 speaks on this directly when it talks about obscene talk, and so, as a Christian who believes the Bible, I seek to follow Paul's instruction by God's Grace.
The problem comes when we ignore the context and audience of this passage. The book is actually a letter written by the Apostle Paul to a church in Colossae; it's written to Christians. Paul is giving instruction on living to Christians. Why is it then that we (as Christians) get offended or freak out when a non-Christian does something that is in contradiction to these instructions? If a Brother or Sister gets frustrated and says something like "oh for christsakes!" we have a right (duty) to lovingly correct them, just like any other sin. Why is it then that we get so upset when someone who is not a believer does the same thing? Yes, it's blasphemy, and it is sinful to take God's name in vain this isn't news to us, but guess what, blaspheming is the least of these people's problems. They're going to hell because they haven't repented of sin (all of it) and placed faith in Christ. They already have the judgement of God on them, what more could our reaction possibly add?
All we are communicating is God's anger, we're not communicating God's grace at all. When we show our overt displeasure at the language of our friends, we're preaching morality, not Gospel. Works, not Grace. At this point, I'm not concerned with the state of your tongue, but the state of your soul.