Okay, think of a bad word. One that you definitely wouldn't say to your grandmother. Pretty bad, isn't it? Perhaps unambiguously so. It may have something to do with bodily functions, excretions, or reproductive activities - or perhaps it is an ethnic slur.
Now, say what that word is in a way that's not offensive, to your grandma or most anybody else. It's not very difficult - there are plenty of substitutes at hand for even some very vile words and concepts. Sometimes those substitutes were developed specifically for use in polite company in the place of their vulgar counterparts.
What is this? Every offensive idea has a non-offensive way of expressing it? Believe it or not, in our society we don't take hardly anything itself as offensive. Rather we have duplicate terminologies - one for polite use, and one for when we intend to be offensive.
Thus to us it is the word and not the thing that is bad, and we inoculate ourselves against the sin of profanity or vulgarity by a careful choice of words. Is this proper? If we angrily and vehemently hector another driver who makes an incautious error on the road, does it matter whether we use good words or bad ones? Arthur Henry King once pointed out that it makes little difference whether he gives voice to his frustrations with "fiddlesticks" or something worse. What matters is the thought and sentiment that gives wings to the word. What matters is what's in his soul. If THAT is vulgar, then so is anything he says, no matter how polite.