It is not necessarily snobbishness to feel a visceral aversion to slobs, where ever they may be encountered. If you have the misfortune to be seated next to one on a long flight whose body odour would repel a skunk, then pity help you.
The underlying import of the old saying 'manners maketh man' extends to the hope, however vain, that others have learnt or will learn, to respect themselves as you respect yourself.