[Note: I don't think Walmart is a particularly bad corporation. I picked it because ernunnos thinks it's a bad corporation.]
Border laws don't cause hardships.
Suppose my house catches on fire. Now you stand at the door with a shotgun and threaten to kill me if I leave. If I die in the fire, have you caused me harm? After all, you didn't kill me, the fire did.
Assumes that individuals have no say in their own governance, and no ability to determine their own political and cultural environment.
Do you think that Walmart's policies would change for the better if everyone were forced to shop there? If not, why do you think that a country's policies will change for the better if the citizens are forced to live there?
After all, you could try to change Walmart's policies the same way we do in politics. Write letters to the BOD, and the president of the company. Buy stock, and vote your stock in the way that you think that the company should be run. Unless you have a lot of money, good luck with that strategy.
Or you could just take your business elsewhere. You immediately get what you want, without spending enormous amounts of time and money trying to change a huge monolithic system. And if enough people shop elsewhere, then Walmart will either change their policy or go out of business.
I think people should be as free to choose their government as freely as they choose where to shop. You want to force people to live under the political Walmarts of the world.
Moreover, it's easy to say, "Why don't you Mexicans just reform your government?" You're in the top 1% in world wealth, yet how would you respond to someone who said, "Ernunnos, you live in a democracy, why don't you stop your government from [implementing insane policy X]?"
Now suppose you're a Mexican making $8/day. How exactly are you going to have the time and energy to pursue politics? Most people in such circumstances are going to spend most of their time just putting a roof over their head, and a burrito on the table.
The more Mexicans who get high-paying jobs in the U.S., the more money they can send back, the higher the standard of living, and the more time and money there will be left over for activism. And if it weren't for border laws, more Mexicans would move back permanently, after making their fortune in the U.S.
Moreover, if you've always lived in Mexico, how are you going to know what a "good" institution looks like? The more they're exposed to U.S. culture, the more they come to expect that their institutions should operate efficiently, without corruption.
Your policies would prevent all of that from happening.