There is a portion of the brain, I think in the frontal part, that controls your ability to stop yourself from inappropriate speech. As you age it deteriorates, and some people never understand that they are saying offensive things. I think there are some out there, who have always been offensive, and it just gets worse as they age. Some of them justify it when they are younger as 'just being truthful' when they are just being tactless. I personally prefer a little white lie and being told what I did was just great!
Phyllis