Andrew, you write that “peer pressure is mimetic; but not all mimesis is peer pressure”. This is absolutely correct, mimesis is like gravity, we live in a sort of web of mimetic desire, and this is what makes us human. Peer pressure is just one of its frequent and diverse manifestations.
“The pressures exerted back and forth among parties who are equal in all relevant respects—will inevitably be bad. Excessive similarity leads to violence”. What you are describing here, Andrew, is what Girard called internal mediation, or what Freud referred to as “the narcissism of small differences’ and has to do with the proximity of the rival parties, i.e. social, or physical closeness etc, this could be a parent, or peer or someone in our immediate life setting. It is also called ‘undifferentiated’ society, and violence will result easily from mimetic rivalry in these circumstances. External mediation, on the other hand, is when there is distance from our life setting, albeit physical, social etc, which eliminates the possibility of violence. The classic example of this, is Cervantes’ ‘Don Quixote’, whose life is modelled on Amadis of Gaul. The violence of mimetic rivalry is impossible in these circumstances, as Amadis was a mythical character.
Your refer also to peer pressure as ‘inevitably bad’, but René Girard did not hold that mimetic desire is inherently bad or destructive. In his book ‘Deceit, Desire and the Novel’, Girard referred to situations when the majority unites in telling the truth to an individual. In a reflection on Stendhal’s book ‘The Red and the Black’, Girard writes about the character M. de Renal, who believes a lie and refuses to come to the truth. Girard writes, “The situation is now inextricable. Even if the whole world were to band together in order to convince M. de Renal of the truth he would refuse to accept it”. Girard knew that there were times when the larger group told the truth in a way that did not scapegoat.
Girard speaks of the possibility of “good contagion” or “nonviolent imitation”, which can come about through a fundamental change of personality through the imitation of God or Christ. Imitatio Christi; imitate the good.