This guy says that I can not know what type of oil is used for making chips because the company's might put something vegetable-oil on the productlabel eventhough they use animal based fat. So I told him that they always have to put right information on the label because they get sued when people get hospitalized when they have allergies.

Is he really stupid or do you believe that company's lie to consumers?

Well, it may depend on where you are. In the US, I would be pretty surprised if a label said "Vegetable oil" when some sort of lard was used. However, not all non-vegan products are allergy risks, at least not equally. Fish, eggs and dairy should always be labelled, since many people have severe allergies to them. Otherwise, when it comes to oil, a meat product could be fried in the same vegetable oil as your french fries or potato chips, and it would look the same on any label.