Considering the torrent of abuse the church suffered in the very beginning, the writings of the earliest fathers do not reflect a lot of reactive theology or statements but rather focuses more on the virtues of Christianity and the love of Christ. The defensiveness appears to have come in later with the infiltration of heretics on grander and grander scales.
I would definitely say I experienced more defensiveness and divisiveness in the Eastern Orthodox churches than in the Oriental Orthodox churches. The Greeks particularly seemed to emphasize the difference between them and the Catholics; but that may ultimately be an Italian/Greek thing as opposed to an Orthodox thing. Another factor may be that most Orthodox churches have spent many centuries being oppressed by an foreign occupant and we are observing the residual affects of oppression rather that the inherent mentality of the orthodox mind.