I don't think we can generalise all small businesses.

There is this vegan groceries close to my place, the only people working there are the owners, a husband and wife. They don't exploit anyone and don't intend too, and they give half of what they earn to animal right associations.

Obviously don't steal from those.

If on the other hand you know of a small business that treats their workers like crap, makes them work crazy non paid overtime hours, then go wild and fill your bag.