those laws, and right now they are insufficient for the challenge at hand...i.e. a sustained surge in the number of immigrant petitioners at our border. Our laws need to be changed in many ways to resolve this increase...i.e. decisions on the total number to be accepted...from which locations...for which reasons...how to humanely treat them...deport them, if necessary...as well as protect ourselves from those who could do us harm...in short, we need Congress to pass a bill that makes these decisions, and provides sufficient funding to make it happen.
Fortunately, we have a bi-partisan Senate Bill that addresses virtually all of the most important issues involved...but we have a Malignant Narcissist and his followers who have chosen a political talking point over a resolution to the Border Crisis.
As for why Dems are thinking the way they do...they happen to view immigrants as human beings in need...not unlike their forbearers...and, it can be fairly stated that they think a lot like Catholic Church does...as this excerpt from the document "Dignitas Infinita" urges...
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The work of emigrants
40. Migrants are among the first victims of the many forms of poverty. Not only is their dignity denied in their own countries, but their very lives are put at risk because they do not have the means to create a family, to work or to feed themselves. Once they arrive in the countries that should be able to receive them, "they are not considered worthy enough to participate in social life like anyone else, and it is forgotten that they have the same intrinsic dignity as any other person. [...] It will never be said that they are not human, but in practice, with the decisions and the way they are treated, it is expressed that they are considered less valuable, less important, less human". Therefore, it is always urgent to remember that "every migrant is a human person who, as such, possesses inalienable fundamental rights that must be respected by everyone and in every situation". Their welcome is an important and meaningful way of defending "the inalienable dignity of every human person regardless of origin, color or religion".
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Note that the GOP candidate for President does not share this view of immigrants...your choice, Curly.