We find all kinds of people in this world and the ability of our society to continue to produce an endless supply of people who don't know "crap" is simply amazing.
After a career spent trying to convince people to purchase my goods and services I have found that it isn't usually what you say to someone, it is how you say it.
In the case of the OP's slob encounter, I might have said "I've found that job is a little neater and less stinky when I use my hose". All while smiling and going on about my business.
But I don't feel an overwhelming need to educate adults, who by their actions, have already indicated to me that they are too stupid to have lived to be adults. Opinions may vary, but I like mine. LOL