Debating by its nature, unfortunately, focusses less on determining the truth and more on beating the other side. The propositions advanced and assaulted were prodigious in both number and import. Immigrants steal jobs from the native-born. Immigrants take unwanted jobs that the native-born won't touch. Educated immigrants provide high-level expertise, i.e. in electronics and health care, for lower cost.
Immigrants place an extra burden on the welfare system.
Immigrants generate more taxes for welfare than they use up. Immigrants put a strain on already overstrained resources. Immigrants create new markets. Immigrants import crime. Immigrants are, in the vast majority, law-abiding.