HEY COPS! Dude is carrying a substance quite flammable in both liquid and vapor form! SHALL WE HIT 'EM WITH THE ELECTRICAL WEAPON OR NOT?
Well, what's the alternative? I'm thinking you might not want to count on the effectiveness of pepper spray against someone who sniffs gasoline for fun. Wrestling with a dude covered in gas is out of the fucking question, and I imagine shooting him would be considered excessive.
Man, I want a public access cable show. "OK. Next up, I'm going to need a gallon of gasoline, a taser, a fire extinguisher, and a volunteer from the audience."