Kids have the darkest humor

Unless they're lactose intolerant. Then their last moments before death will be the gassiest, most shitty moments.

A child didn't write that.

Clearly adults writing

think its got to do with polarity. Water is polar and can't "affect" (can't think of right word atm) certain substances while milk is non-polar and can therefore "affect" other these. I know, eg. with chili, if you eat hot chili its best to drink milk as water with just swirl it around whereas milk will help wash it away.

Milk will dilute the pH of the cleaning product making it non-acidic so the child won't die