It may not affect most sle patients, but if you have had episodes of vasculitis, or stroke, I would advise staying away from anytihng that would trigger it..
I liked the tea alot- until I had a mini-stroke. I work in the field of nutrition, and have a lot of professional resources at my fingertips (literally). Mate is used by millions of people, and you'll always hear both sides of the issue. Just be informed, be aware of what your triggers are and learn to spot an upcoming flare before it's out of control.
Good luck!