You need to turn off anti-aliasing for Dolphin in your GPU's drivers.
You're using a rather outdated version, by the way. Using the latest beta version or newer is recommended. The latest builds do still have this behavior (though the message has been made clearer), but there have been lots of fixes to other areas of Dolphin.
You're using a rather outdated version, by the way. Using the latest beta version or newer is recommended. The latest builds do still have this behavior (though the message has been made clearer), but there have been lots of fixes to other areas of Dolphin.