Because it's not level-field competition
First off, when has business ever had level-field competition ?
Take a look at small store and shops; they have almost completely vanished in major metropolitan areas, being replaced by large Department and Chain stores. How can a local hardware store compete with Home Depot ? Very simply most can not ! They can not match the pricing nor selection available at Home Depot.
Does the public say, "Hell I don't mind paying an extra couple of bucks for a hammer, I am going to support local shop owners", some people might, but the vast majority do not.
So what do we do, outlaw Home Depot ?
Now let us look at consumer electronics, I can remember a time when there were numerous American Manufacturers, which have now all but disappeared, why ? Simply because people bought foreign made products due to their lower prices, again did people say "hey, I'll spend the extra money and buy an American product and if it is out of my price range then I will just wait and save for it", no they bought the foreign made one.
It is a similar situtation for Corporations, they shop to get the most for their money also, no more selfish than the general public, yet they are judged by a different standard, is that really fair ?