Oh, I don't necessarily have a problem with Mia having HIV. Winick aside, it's somewhat plausible given the fact that she was a prostitute. And yeah, the disease is infinitely more treatable nowadays than it was "back in the day"; that's not my issue.
I'm just against the fact that she's now on the front lines of a battle that can have lots of unintended results/casualties. A vigilante that doesn't ever bleed "on the battlefield" is about as likely as a paperless bathroom. She's endangering those she works with, those she's trying to save, and those she's trying to stop, especially if she doesn't tell them she's HIV+ (like, say, the Titans back when she was with them) and that's unacceptible to me.