Online: I put the member on "ignore."
Offline: I address the snark if it directly effects my job or friendships. Otherwise if it doesn't effect either, I ignore it.
I've had to deal with a lot of bullies over the years b/c I have was raised as a doormat/codependent/scapegoat of my family system. So, I've spent my whole life fighting that "programming" with the help of therapy and using interpersonal situations to practice what I've learned. Sometimes I'm successful, sometimes not.