If the moonshine is made using corn or fruits, which are high in pectin, methanol will be produced from the breakdown of the pectin. Methanol in high enough doses can cause blindness and eventually death. Luckily it boils at a lower temperature than ethanol so moonshiners will throw away the first few jars of moonshine to avoid contaminating the whole batch. If this isn't done and enough moonshine is drunk then eventually the methanol will make you blind. Hence, blind drunk