@medinabuckeye1 I think there is a certain psychological phenomenon that occurs when someone "converts" to something, particularly later in life.
It's seen of course in religion (or losing one's religion). But it's also seen in a lot of other places. Have you ever known someone who became vegetarian or vegan and just won't shut the f&$k up about it? Or joined Crossfit and will tell you how AMAZING it is and how your life will be transformed if you join too?
I think people have a certain inertia in their choices/beliefs in life, and the amount of lift to overcome that inertia to change is usually very large. And whatever pushes them over that inertia must be powerful enough that they believe others should follow. Because once they "saw the light", they can't understand how others don't see it the same way.
I don't see this behavior from people raised without religion. I don't see it from people who [based on their ethnic traditions, like many Indian people or Jews/Muslims] were raised not eating meat or not eating meat from particular animals. I don't see it from people who have spent their life with fitness as a hobby. But I see it from people who "change".
So if you've been raised your entire life in a religious tradition and as you mature you come to the conclusion that everything they told you was a lie, it can cause you to feel betrayed and angry. God is supposed to be the center of your worldview, and you lose belief it even exists.
It's an identity-shaking change. And then when religion continues to pervade public life,
particularly in political life, and people are trying to make policies that affect you based on their belief in that "lie", it fuels that anger. It can feel like religion is continuing to poke YOU in the eye with that lie. And some people can't get over that, so they react emotionally.
You're asking the question of why they behave that way, as if they are behaving that way based upon rational reasons. I think you may not be understanding that this behavior is driven by the id.