van drivers don't pick fights with irrelevant and annoying flies. Your mate must have done something that caused offence.
The vast majority of Van drivers are mild mannered and middle-aged, only the younger lot are likely to engage in a fight, and even then they know there's a risk to it so will only do so if triggered by someone being particularly confrontational and abusive.
Disclaimer: My father is a van driver and has been for 40 years. I've been to rallies when much younger, and I never saw any of them needlessly get violent. They're a perfectly reasonable lot and don't differ greatly to the culture of this here cycling community.
Arf arf!