Skepticism about immigration economics

The London Guardian reports:

Nowhere is this more vividly manifest than with immigration. The thinktank British Future has studied how best to win arguments in favour of immigration and multiculturalism. One of its main findings is that people often respond warmly to qualitative evidence, such as the stories of individual migrants and photographs of diverse communities. But statistics – especially regarding alleged benefits of migration to Britain’s economy – elicit quite the opposite reaction. People assume that the numbers are manipulated and dislike the elitism of resorting to quantitative evidence. Presented with official estimates of how many immigrants are in the country illegally, a common response is to scoff. Far from increasing support for immigration, British Future found, pointing to its positive effect on GDP can actually make people more hostile to it. GDP itself has come to seem like a Trojan horse for an elitist liberal agenda. Sensing this, politicians have now largely abandoned discussing immigration in economic terms.

All of this presents a serious challenge for liberal democracy. Put bluntly, the British government – its officials, experts, advisers and many of its politicians – does believe that immigration is on balance good for the economy. The British government did believe that Brexit was the wrong choice. The problem is that the government is now engaged in self-censorship, for fear of provoking people further.

There is nothing wrong with quantitative evidence, when done right, but the public can recognize that the govt is lying about benefits of immigration.

The British claim that immigration has a positive effect on GDP, but the same arguments says that crime is good because it causes us to spend more money on prisons and law enforcement. It neglects effects on the quality of life, and on long term effects. It is like saying negro slavery was good because it boosted cotton production.

The biggest current controversy is about Syrian immigration. Can anyone tell me specifically how such immigration has any positive effect on Britain or the USA at all? Where I live, most of the social problems are traceable to immigration.