In my conversations with your average Stuff White People Like (SWPL) liberal, most of their arguments for MORE illegal immigration & amnesty seem to be centralized around their hedonistic and leisure impulses. For them, illegal immigration means they get to pay a pittance for lawn care, house cleaning, and other manual labor. It means that if they have kids, they get a cheap nanny to watch their child while they live the life of the hip young cosmopolitans. They get to enjoy 'cultural enrichment' in the form of the most authentic Central American food.
The idea that many Americans aren't involved in their white collar lifestyle and suffer from increased competition from illegal aliens never seems to bother these SWPLs. The idea that they should have loyalty to their countrymen is a charming but outdated idea to them at best, krazy kracker konservative konversation at worst! As Steve Sailer has pointed out, many liberals have leap frogging loyalties as a form of status oneupmanship among other liberals. Worrying about something like the welder down the street doesn't earn you libcred among the rest of the coop - how many Somalis have YOU sent food to?
Conservatives tend to have concentric loyalties, which makes a lot more sense as they're naturally developing (my family, my faith, my town, my state, my country, my race) versus the artificial liberal loyalties that seem to go: my ideology, poor oppressed colored people worldwide. This isn't a new thing - people starved in China while Mao shipped corn to Eastern Europe in the name of "Worldwide Communism" while in the middle of a pissing match with the Soviet Union. It seems to be a natural concurrence with the leftist worldview.
Leftists also seem unable to fathom a 'social cost' to massive illegal immigration, as the idea that there's a social cost to anything except racism or transphobia or whatever their cause du jour is doesn't register with them. Failing in school? Well that's because of racism, it has nothing to do with race. Lots of single moms and the disintegration of the family unit? Oh well that's because of the Vatican! Living off welfare and foodstamps? Well we need to tax the rich more! More crime? Well that's because of the police being racist!
As you can see, leftists have plenty of answers for everything. Its just that they're fucking insane and wrong and would rather blame their countrymen then the real factors because then the elaborate mental house of cards they've built for themselves would come tumbling down around their ears. The fact that their choices result in more inequality as they build up whitopias for themselves is lost on them. Its all about appearances, but those of us in the real world have to fucking deal with the results of their games of status.