I may not have much of a southern accent, but the fact I was born and raised in the great state of Georgia gives me carte blanche to use the phrase "bless your heart" at free will.
According to Urban Dictionary, "bless your heart" means:
1. A polite way to say "go to hell"
Bless the heart of the attorney I dealt with on Monday...
Me: We are at the court house now and the judge won't sign the divorce papers because you left out an address.
Attorney: What exactly is missing?
Me: [reads checklist provided by judge]. The judge said if we can get something to her right now, she'll sign it.
Attorney: There's no way it can be done right now. I can pull something together and mail it to you.
Me: No, it needs to be done right now. The judge said it could be done. We paid you $1200 to get this right and you need to fix it.
Attorney: Ma'am, every county is different and there is no guarantee that we will get it right the first time.
Me: Then what did I pay you $1200 for?!?! I'm gonna go ahead and hang up now before I say something I will regret.
Attorney: Well, ma'am...I'd really like to help you.
Me: Then hang up the damn phone.
2. A term used prior to ridiculing, insulting the sensibilities of, or pointing out the shortcomings of someone. Used to soften the blow of a statement, and can render nearly any comment, no matter how brash or distasteful, socially acceptable.
Spoke to a former co-worker of the above attorney. She asked if he was rude to me.
Bless his heart..."He was too stupid to be rude."