A man wished to purchase a Donkey and decided to give the animal a test before buying him. He took the Donkey home and put him in the field with his other Donkeys.
The new Donkey strayed from the others to join the one that was the laziest and the biggest eater of them all.
Seeing this, the man led him back to his owner. When the owner asked how he could have tested the Donkey in such a short time, the man answered, "I didn't even need to see how he worked. I knew he would be just like the one he chose to be his friend."
Moral
There's no getting around the fact that this story is about judging. While we like to be judged on our merits, the fact is we're likely to be judged based upon other things.
We might want to make the useful distinction that while a person is apt to be judged by the company he / she keeps, that doesn't mean you have to choose to be like the company you keep.