Someone who doesn’t understand “taking the Lords name in vain” shouldn’t be lecturing anyone about it.
It has nothing to do with obscene talk (see the book of Ezekiel) and everything to do with swearing / taking an oath in the name of the Lord you have no intention of keeping (or no ability to do so) said oath. It can also be in the context of being a witness and ‘swearing to God’ you’re telling the truth - when you know you’re not (see Jezebel and her lying witnesses).
Jesus literally touched on this very topic.
““Again, you have heard that it was said to an older generation, ‘Do not break an oath, but fulfill your vows to the Lord.’ But I say to you, do not take oaths at all – not by heaven, because it is the throne of God, not by earth, because it is his footstool, and not by Jerusalem, because it is the city of the great King. Do not take an oath by your head, because you are not able to make one hair white or black. Let your word be ‘Yes, yes’ or ‘No, no.’ More than this is from the evil one.” Matthew 5:33-37 NET