I can totally understand how someone could be a professional performer like an actor and still have social phobia. I have performed in various ways, singing, dancing, giving speeches, teaching etc on numerous occasions and I experience less anxiety than the average person in these situations.
Unfortunately, once I actually have to interact with people, I have lots of problems. I would say I have specific rather than general social phobia, but over the years it has got wider and wider. Still, it doesn't really happen when I am in front of an audience because then I feel in control, and audiences are (in my opinion) more predictable than small group interactions.
It is kind of frustrating sometimes. I sing in a choir and I am at least ten times as worried about going for a quick drink at the pub after the concert than I am about performing in the concert itself, even when the concert is being recorded for public broadcast and the music is really difficult and there are so few people that the smallest mistake will be obvious. Go figure. :roll:
So I could easily believe that some actors could have social phobia.