Sometimes a child is delighted by habits that adults regard as ‘rude’ such as nose-picking or staring hard at someone who looks remotely odd. For instance, if the man sitting opposite in the bus has a big nose and she keeps pointing at it and saying ‘Nose!’ then your only hope is to cause a diversion: pretend you’ve seen something interesting outside the window.
Oftentimes, children draw the stares to themselves, by delightfully unselfish-conscious physical habits such as scratching of the crotch. You have to urgently come up with a diversion because if you lose your temper and speak too harshly to the child, then you may not only draw attention to the disgusting habit, but precipitate a tantrum, which of course is even more embarrassing.