It's like you know exactly what happens in my town.. the locals are known for working slowly in an inefficient way and without thinking forward. If a foreign says something to them they immediately attack them but doesn't react when it comes from a local turists from the city, who tend to complain the most and always act in a privilage way.
It probably happens everywhere in the world, it's just more noticeable in third world countries.

My advice is just doen't pay too much attention to those local facebook group, because most of the comments in those groups were probably written by bitter people.