system
Given the following post, respond as if you're commenting on Reddit:
human
I support free migration, and believe that all immigration restrictions are unjust. CMV

Counterarguments to common arguments against open borders:

* "Immigrants would take jobs that should go to natives." Regardless of whether immigrants are taking jobs that would otherwise have gone to natives (the empirics I've seen lead me to believe that they don't), why should being a native entitle anyone to a better chance at a job? Suppose someone made a similar argument against women in the workforce - "Women shouldn't be allowed to work because they'll take jobs from men" - or against efficiency - "People shouldn't be efficient and productive because then it takes fewer people to do the same job". If an employer wants to hire a native worker, and the worker is capable of consenting to taking the job (i.e. is not a child or extremely mentally unhealthy), then they can agree to a mutually beneficial contract. This is uncontroversial (except among the far left), so what's different if the worker happens to live in another country?

* "Immigrants would change our culture." Immigrants have changed American culture in the past, and no one today thinks that's a bad thing. More importantly, culture is no more than what individuals who live in a certain area or identify with a certain group tend to do. If some native-born Americans suddenly adopted different cultural norms, no one would support deporting them.

* "Immigrants would abuse the welfare state." There are two answers to this. The first is that it would not be difficult to restrict the welfare state to citizens. The second addresses the purpose of the welfare state. If the purpose of redistribution is to benefit the unlucky (those who happen to be born into low-income families or lose their jobs through no fault of their own), then people who are born in third-world countries are even more unlucky than either of those groups. If they come to first-world countries and work, they would be more productive than they would have been in their native countries (not to mention they could be fleeing things like wars and genocide), and, in a utilitarian calculus, the benefits to these immigrants far outweigh the benefits of the welfare state to those who are already wealthy by global standards.

* "Immigrants would increase crime." I've not seen much empirical evidence to justify this claim. Yes, there are some places with many immigrants (or children of immigrants) that have high crime rates, but the same can be said of natives - plenty of high-crime areas don't have any foreigners. And even if immigrants are disproportionally likely to commit crimes, that is not an argument against immigration unless you also believe that native-born groups who are disproportionately likely to commit crimes should be deported as well.

* "We live here, so we decide the rules." Even if that's true, what's good about current rules? The above arguments show why current rules are bad (or at least internally inconsistent), so why not change them? More fundamentally, though, why do you get to decide the rules? If I own a house and want to rent it out to an immigrant, under what authority can the government say that I can't? Does it own my house? If so, how did it come to own it? If I am a business owner and want to hire an immigrant, and the immigrant wants to work for me, what authority does the government have to stop a mutually beneficial voluntary exchange? Does it own my business? The country is not owned by the government, it is a composite of a large number of properties with different owners, administered by a government. Government is a service, not an owner - if you always hire the same plumber to work on your pipes, that doesn't mean he owns them, so why is it different for government?

Edit for another common counterargument:

* "Open borders mean you don't know who's coming and going." "Open borders" doesn't necessarily mean "no borders". Under open borders people could still have to register before entering a country, it would just mean that they wouldn't be denied entry once registered.
gpt
Money is the key ingredient in immigration restrictions. Citizens pay taxes and get the benefits of those taxes. Immigration restrictions are in place to guard against illegal immigrants coming into the country and benefiting from the citizens tax money. 

Also, educated immigrants are usually a good thing because they bring something to contribute to the society - hence why they can usually get citizenship faster. Uneducated immigrants are beneficial too, but only to a certain extent. They provide cheap labor but suck up resources they usually can't pay for. So it's a pretty grey issue, but immigration restrictions are there to protect tax dollars.