How many curse words or phrases - that are now considered by many / most as cursing - have that label due to a frequent use in a "cursing" manner?
Naesala, I would agree with your assessment that racism and classism have contributed greatly to what developes a word's "curse" label, but both of your explanations rest on the same foundation - original use in a derogatory or demeaning manner. Basically, the intent behind words and phrases determines what is considered offensive, vulgar, or obscene. For example, if enough people begin using the word "smart" with disdain and only in situations where insult is conveyed then I submit that "smart" would begin to gain a reputation as a curse word.
Conversely, words that used to be used only in instances to convey insult or disdain (the likes of 'damn', 'crap', and similarly viewed words/phrases) that are now more frequently used for humor or simple casual conversation begin to lose their "curse" status.
As to the aspect of "to curse or not to curse", it is the free will choice of each individual as to what words to use, but more importantly
every word used comes with the choice of
HOW to use it.
Not to get too "religious" or spiritual on this topic, but even the Bible does not outline _what_ words or phrases are cursing or 'forbidden' but rather the mindset and intention being the key.
... This brings to mind a question I've long had: can anyone explain to me why some people insist that certain words themselves have a permanent curse or 'bad' word nature to them?