....might want to think about the amount of bleach they throw around their houses or the factory farm fed animal products they feed their kids.
Not saying that if you do one, you do the other but rather that people obsess about relatively (mostly) harmless dirt but yet can be indifferent to other 'pollutants' (for want of a better word) that are carelessly thrown at themselves and their families and are a lot more harmful than mud, sand or microscopic particles of dog poo left by some heinous person who didn't remove their shoes in the house!