Is it bad to wash a car with body soap?

What do you mean by body soap? Soap that is in bar form, or soap that in a bottle like body wash? Bar soap could pick up sand and grit that might scratch the finish. Body wash is a mild abrasive but I have never heard of anybody using it for washing a car but I assume that a slight clouding of the clear coat is possible. If you have access to dish soap (detergent) it is the best improvised automotive soap.