Words are simply symbols we have agreed upon to represent things.  As Silver and Jade Tears said, they, in themselves, are neutral.  We assign value to them depending upon our past experiences, frame of reference, value system, etc.  So, using her example, murder may be bad to me, but to a person who views life as nothing but dispair, it may be good. 

Of course there are certain 'trigger' words which are used to get a specific reaction.  They are more emotionally loaded than other words, but again, depending upon the listener, can be either positive or negative.  Example: mom, apple pie and the American flag...

As Lewis Carroll asid, when I use a word, it means exactly what I want it to mean.  You may have an entirely different picture in your head when you hear it.  And therein lies the whole fascination of interpersonal communications!