This might help:
The Drama Teacher's Research Room
http://www3.sk.sympatico.ca/erachi/

or try Scott's Theater Links
http://www.theatre-link.com/

Personally, I've never really felt that theater per se is necessary to the human psyche, rather that some form of self-expression is important, particularly in socially organized groups. In which case, the arguments that apply to art in general probably apply. A general group discussion of the need for self-expression as it applies to theater and the performing arts may be beneficial.

Of course, my argument is compromised by that fact that I never bothered to think of theater in the broad sense, except as a way for people with common interests to get together and have fun. :)

Anyway, I hope I've been able to help in some small way.

Mike Polo