So they don't feel that they need to present any evidence for the existence of the Christian God. Instead, they argue from the "impossibility of the contrary". They claim that without God you can't make sense of the world and you can't account for things like the laws of logic, mathematics, and universal laws of morality. They'll say that if you reject the Christian God, your worldview is reduced to absurdity. They deploy what they call the transcendental argument for God or TAG for short. Essentially, they say that the proof of God is that without him, you couldn't prove anything because non-Christian worldviews can't account for the laws of logic. Since the vast majority of people that the prsuppositionalist deals with are not philosophically sophisticated, they stumble and bumble and contradict themselves in attempting the task and the apologists steps in and says see I told you so. This is why I think their methods are unethical, because they prey on the philosophically ignorant. The whole edifice is simply an argument from ingnorance, in my opinion.
Imagine going up to some 18 or 19 year old and asking them to account for the "immaterial" laws of logic, mathematics, and universal morality. Do you think they could do it in an informed way.?