The purpose of a system is what it does, and to quote Stafford Beer, there's "no point in claiming that the purpose of a system is to do what it constantly fails to do".

If immigration law and border policies are much more succesful at brutalizing immigrants than taking actual steps to curb illegal immigration or let alone the hiring of illegal workers, then regardless of what people claim the intentions behind those systems are, their de facto purpose is to be cruel and deadly