We help contribute to curbing it, and I think it's worthwhile for people who want to contribute (aka charity), as well as disaster relief assistance, but beyond that I don't think federal aid is warranted save in very special circumstances.
I can't say I've seen anyone on "the left" argue that mass immigration is the solution to world poverty. This is the only guy I've seen on any talks or speeches who even claims this is a thing. Yeah, we're not going to make a single dent in world poverty by letting lots of people in. He's arguing against a strawman, something easily knocked over because... everyone knows it's true.
The thing is, we're willing to take in people who are WILLING TO WORK HARD to make a better life for themselves.
"We take in one million immigrants a year, that's nothing compared to LOOK AT ALL THESE GUMBALLS".
The point is that those 1 million people are leading better lives than they were, not because we're solving world poverty. He's pointing to the massive number of gumballs who get nothing out of the deal, meanwhile trying to say that 1 million people a year having better lives because they want to work is "nothing" because LOOK AT THESE GUMBALLS.
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You can't even answer the question of who "some people" are in the statement "some people say that immigration can end world poverty". Sad.