The zealot truncates the truth, minimizing or stripping away the element of love, leaving behind only assertions and reason and perhaps little of it. Truth becomes something to be debated and people who hold different views become enemies whose arguments must be hamstrung and smashed. Communication therefore becomes adversarial and combative rather than relational. Instead of a thing of beauty to be desired truth is presented as a sword that destroys. Overall, there is a drift in goals away from witnessing to truth toward destroying opposition to truth, even at the cost of wounding or killing people with contrary views.
Arrogance drives out humility.
There is no allowance for the need to grow in understanding of truth in all its dimensions, subtleties, and application to specific situations. Unfortunately these limitations are neither recognized nor acknowledged when pointed out. Truth is proclaimed without mature understanding and applied without sensitivity. The process is self-insulating because information that might challenge these limited understandings is either not perceived at all or so badly distorted and caricatured that it can have no impact. The fact the others disagree is seen as evidence of weak intellect, sinful perversion of character, and ultimately unworthiness even to exist.