I've met up with groups of social anxiety people twice. Very uncomfortable, and I felt completely out of place, unable to relate to them (though they were good experiences anyway just to have tried and found out what it's like, and I'll do it again someday). It helped me realize that I'm as alien to people with SA as I am to anyone else (or nearly so -- no idea how horrible a similar meeting with non-SA people might be).
There are dozens of different sorts of social anxiety which are really quite different, so you wouldn't even necessarily find much to relate to there.