Libertarians believe in an easier pathway to citizenship.
Throughout the history of the United States, we have welcomed and embraced immigrants. This is a nation of immigrants, comprised of one of the most diverse populations in the world. Immigration has been on ongoing issue in Nevada, and failed immigration laws have fostered hostility against immigrants.
Immigrants come to the US in search of greater freedom and opportunity to experience the "American Dream." Many Americans have ancestors that immigrated to the US through Ellis Island. When they arrived, the process was very easy to become an American. Less than 1% of immigrants were turned away.
Real threats can and should be addressed without creating so many unnecessary obstacles for citizenship. Throughout our history, immigrants have been good for the economy and immigration actually creates more jobs than immigrants account for. Immigrants have a higher workforce participation rate than natural born Americans.
The most efficient use of resources to prevent terrorism, smuggling, or other crime, is to investigate terrorism, smuggling, or other crime. Monitoring the millions of innocent people who cross the border for other reasons (and forcing innocent people to sneak across far from observation--where we can otherwise look for real criminals) is wasteful and counterproductive.
The only harm and costs related to immigration are the ones associated with government efforts to prevent immigration.