Whether consciously or subconsciously, psychologically unified groups always develop a cultural norms which defines what it means to be “one of us”. This code may include ideological tenets, duties, forbidden practices etc… Tampering with this code is dangerous, but sometimes absolutely necessary.
Conformity to cultural norms is rewarded with social validation. Nonconformity is punished along a spectrum ranging from verbal condemnation to expulsion. This mechanism operates directly on the dopamine channel, and plays a preponderate role in human behavior.
Dopamine is a neurotransmitter that operates on the reward, pleasure and motivation mechanisms of the brain.
Social validation causes dopamine levels in the brain to increase, creating a sense of happiness and well being. Social condemnation has the opposite effect, and can be emotionally devastating. This is the biochemistry of the conformity instinct. Very few humans are strong enough to resist its pressure. As such, most integrate the cultural code of their group as a package, conform to its expectations and reject or punish those who don’t.
In its most rigid form, cultural code has the force of morality, and is utterly intolerant of dissent. Criticizing or questioning its tenets is interpreted as an attack on the group, and by extension the self. The defensive (or aggressive) reactions that typically follow are the ideological equivalent of an immune response.
Tolerance in and of itself is not enough to counter this dynamic. New cultural norms must be established. To accomplish this requires strong, positive leadership.