Благодарю заранее.

See:
http://forum.wordreference.com/showthread.php?t=1144977

Re: to tar the whole region with the same brush

Basically, to tar somebody or something with the same brush means to blame a group for something just because of the actions of one of them.

So, if a child at school misbehaves, the whole class gets punished.

There are subtle variations of meaning in different contexts, but that's the nub of it.

"To tar the whole region with the same brush" sounds as though somebody is judging a whole region by the attributes or activities of a small part of it.