The point is that, in the South, sweetie isn't a gendered term. I'm a man and get called sweetie every day in a non-demeaning sense. When used pejoratively, it's essentially "bless your heart" condensed into a noun.

Interestingly, at least in my area, it's generally only used by women and effeminate gay men. As a result, actually using the term does imply effeminacy, so a straight man using it to insult a woman may be unknowingly implying something about himself which he'd find embarrassing.