Calling out the cigarettes but ignoring the next line about kerosene.

If you did them the other way, kerosene then cigs, well that would burn the parasite out, sure, but the host… well, it might hurt a little.

You can drop a lit cigarette in kerosene and it will just put the cigarette out. You can also so that with diesel. You cannot, however, do that with gasoline.

You cannot, however, do that with gasoline.

Yes, you can. A match or a lighter will ignite gasoline vapors. A smoldering cigarette will not.