Basically, someone near their little demonstration ran into something or stubbed his toe and exclaimed "Jesus!" The Christian group was appalled and asked him to repent his sin, for he had "used the Lord's name in vain," at least according to them.Thou shalt not take the name of the LORD thy God in vain; for the LORD will not hold him guiltless that taketh his name in vain.
My stance is that I disagree with the idea that this line means "don't say God or Jesus under any circumstance outside of prayer." I think it's absolutely silly to censor your use of the word "God" or anything, and I certainly don't think the Bible intends this to mean saying Jesus's name out loud is a sin. Rather, I am under the impression that what is being referenced here is the profane use of God's name in a less direct sense. That is, I think it is forbidding the use of God's name or message to make immoral personal gains or to harm others.
For example, using the lord's name as a televangelist who makes millions of dollars off of suckering people into giving you their hard-earned money.
Any number of other scams involving God's name, including those people who claim to be able to make you rich off of their "Godly" investment, or paying for miracle healing.
Utilizing God to gain power/control. I see this in particular being what the Bible warns against. Those who use Christianity to gain power are dangerous people indeed. Throughout history religion (and in particular Christianity) has been used to control the masses and gain political control and influence. Even today, politicians who flaunt their "Christian" life are violating this passage, because they are explicitly using God's name to further their own careers and agendas.
I'll stop ranting for now. Any thoughts?