Of course it adversarial. The average VC is in a intellectually weak position whenever they speak to a founder for the first time. The founder has thought about their problem for months, maybe even years, while the average VC might never have thought about it. Suddenly they are faced with responding to the founder and in a manner that allows them to control future negotiations. If they are average they will try to control the situation with aggressive questions that attempt to throw the founder off guard. In this sort of tactic they have far more experience than most founders.