Just about any word can be said to have a denotation and a connotation. The denotation of a word is the object or objects to which the word refers. The connotation of the word is the emotional reaction a word elicits. In the case of euphemisms and dysphemisms one is is replacing a word with another word that has a similar denotation but a different connotation.
In my earlier post on this topic (and in the George Carlin bit included) this was presented as a bad thing; as a debasing and abusing of language. There are, however, many situations where the use of dysphemism and euphemism are appropriate. For example, when talking to someone who has just lost a loved one it seems perfectly appropriate to use a euphemism for 'death' such as 'passed away' or 'lost.' In fact, it would be rude and extremely insensitive to do otherwise. Language is a powerful and subtle tool (arguably the most powerful humans have ever created), and it can be used for much more than the simple transmission of information. It is also the primary vehicle through which we relate to and interact with one another. Just as it can be used to wound and hurt others, it can also be used to heal and uplift. As La Fontaine wrote in his Life of Aesop, language is the best and worst there is.
What I am trying to get at here is that as critical thinkers we should think deeply and sensitively about language, and we should use language to expose lies and deception where that is appropriate, but we should also use it to heal and mitigate pain where that is appropriate as well. The context here is extremely important, and as good critical thinkers we should be as sensitive to that as we are to the words themselves.