Final answer:
Employers did not support excluding immigrants mainly because skilled immigrant workers were valuable to innovation and economic growth, contributed to a positive work environment, and there was legal and public pressure to hire them ethically.
Step-by-step explanation:
Most employers historically did not support excluding immigrants due to a combination of pragmatic and economic factors. Primarily, employers recognized that racial discrimination hindered their access to highly talented and skilled immigrant workers who had much to offer in terms of innovation and economic growth. Furthermore, having a diverse workforce was seen as beneficial for engendering new ideas and creating a positive work environment. Employers also had to consider the legal ramifications, such as fines for hiring undocumented workers under laws like the Immigration Reform and Control Act of 1986. This law mandated that employers verify the legal status of their employees to work in the United States. Lastly, public support for high-earning immigrant workers, who are often seen as contributors to economic prosperity, put pressure on employers to hire these individuals legally and ethically.