I've been thinking about this a lot for the last couple days since I heard about some of the things Trump said. I've wanted to respond since seeing your question but I've refrained because I think it will be hard for me to answer without getting pretty close to violating the 20 year rule.

I'm going to try anyway.

I'd like to bend your question a little bit, because there's an analogous situation to this in American history that I just can't stop being reminded of. It's not a religion, but it's a very similar situation. The discourse you're hearing today is very much like what was being said in the late 1800s and early 1900s related to Chinese immigration. Yes, Chinese isn't a religion, but humour me and the parallels will become apparent.

One of the most significant and often cited reasons for why "they" should be excluded has to do with their inability to assimilate to "our" way of life. You find this brought up again and again during this time by journalists, lawmakers and those employed to enforce the laws (and create a few of their own in the process).

Quoting here from To Be an American: Cultural Pluralism and the Rhetoric of Assimilation by Bill Ong Hing

An important element in the anti-Chinese crusade was doubt that they could successfully assimilate into American society... As immigrants, the Chinese posed the first serious threat to the melting pot concept. They were believed to be immutable, tenaciously clinging to old customs, and recalcitrantly opposing progress and moral improvement.

That should sound familiar. The manufactured thread of obedience to the Emperor kept people scared despite not actually being an issue. The manufactured thread of Shari'a is a good analogy.

Quoting here from Erika Lee's The Chinese Exclusion Example: Race, Immigration, and American Gatekeeping, 1882–1924

While Chinese were considered to be biologically inferior due to their status as heathens and their alleged inability to assimilate in an Anglo-American mold, Mexicans were degraded as an ignorant “hybrid race” of Spanish and Indian origin.

Putting aside the at-that-time very-trendy Social Darwinism, this too has clear parallels. They^1 will not conform to our way of life, they do not follow our God. Thus they should not be accepted.

One more quick quote, this time from Erika Lee's At America’s Gates Chinese Immigration During the Exclusion Era, 1882-1943:

the witnesses continued to emphasize how Chinese were ‘‘permanently alien’’ to America, unable to ever assimilate into American life and citizenship.

This was an incredibly important point for people. The eternal foreignness of the Chinese was pivotal to the discussion. This became a major issue not just for immigrants, but for native-born Americans of Chinese descent. There were calls to deport even those that had been born in the states and, in accordance with the 14th amendment, were unquestionably American. Except that it was questioned, and often.

Very often, American citizens found themselves being questioned and their credentials being doubted by a system that was intent on removing Chinese from America's shores. At the time this was often based on their language ability and other superficial factors like their dress, the idea being that anyone born in America would be able to speak English just as well as white people.

• "But Islam isn't a race" / "But Chinese isn't a religion"

So now I want to get to a point that gets brought up a lot in modern debates and bigotry-apologetics. You will hear people say that they can't be racist because Islam isn't a race. The problem with this argument is that "racism" isn't mean't as strictly "racism" but simply as bigotry, since the whole notion of race is ultimately a social construct anyway. Here too there are some clear parallels between the situation you bring up and that faced by Chinese-Americans and prospective Chinese immigrants during the exclusion period. The notion of "Chineseness" was ever-shifting such that it no longer followed the lines of traditional racial categorisation.

One notable case of this is that of Lawrence Klindt Kentwell who had been born to a Chinese mother and a British father in the Commonwealth, who had attended Columbia University Law School and who was living in Honolulu. He would regularly get waived through by immigration officers because he looked white. As things progressed and the enforcement got tighter, he too became a target of the policies. Another biracial American, Ms J Morton Riggs, faced similar scrutiny, despite her mannerisms, dress and all outward expressions of culture being that of a white American. One again the notion of being unassimilatable comes up.

One more point I'd like to bring up. During this period, as today, there were efforts by members of the maligned community to draw distinctions between themselves and the "bad apples". Any previously existing lines of solidarity dissolved in time, as members of the community began to distinguish themselves from the undesirable members of the larger community. There wasn't the thread of terror, but the notion that "our way of life is under attack" was very much present. This all began as a resistance to manual labourers "taking our jobs" in the mid-to-late 1800s in places like California and Hawai'i, but it quickly became a bigger issue that dictated national policy, and it was the very foreignness of the Chinese and the growing Yellow Peril mentality that allowed things to develop to such an extent that California was effectively calling the shots on National immigration policy.

Additionally, if this is in fact the first time that a religion has been the sole defining cause for limiting immigration, that too has a clear parallel, as the exclusion period was the first time that 'race'/nationality was the sole defining cause for limiting migration.

• Has any major political candidate....

Yes, again with the caveat that it's not actually a religion: During this period most major politicians including sitting presidents supported prohibition and often deportation. Letters to the president/s by those with grievances often fell on deaf ears (blind eyes?), and in the early stages of the exclusion period it was only that the policies were in violation of the Treaty of Tianjin that in 1880 it was not supported, but then of course two years later the treaty had been amended specifically to allow for what became the Chinese Exclusion Act.

Finally, one more aspect of the historical scenario which merits repeating. Quoting here from Qin (cited below) relaying an 1878 address to the House Committee on Education and Labor on February by Joseph Kennedy:

Kennedy also emphasized that the Chinese were not Sabbath breakers, criminals, paupers, ballot-box stuffers, Molly Maguires^2, or conspirators against the public schools. Then turning to the charge of nonassimilation, he argued that the Chinese would assimilate with Americans if they were kindly treated, but the desire to assimilate would undoubtedly vanish like smoke if they were maltreated.

Those who cannot remember the past are condemned to repeat it.

Infallible Mods: Let me know if I should reign in the modern connections. I'm not attempting to give an analysis of modern events, but rather just to show how the historical situation should be familiar to subscribers.

Sources:

• Hing, Bill Ong (2000) To Be an American: Cultural Pluralism and the Rhetoric of Assimilation. New York University Press.

• Lee, Erika (2002chinese exclusion) The Chinese Exclusion Example: Race, Immigration, and American Gatekeeping, 1882–1924. Journal of American Ethnic History.

• Lee, Erika (2003) At America’s Gates Chinese Immigration During the Exclusion Era, 1882-1943. University of North Carolina Press.

• Mar, Lisa Rose (2010) Brokering Belonging Chinese in Canada’s Exclusion Era, 1885–1945. Oxford University Press.

• Qin, Yucheng (2009) The Diplomacy of Nationalism the Six Companies and China’s Policy Toward Exclusion. University of Hawaii Press.

• Zeller, Theresa J (2013) The Chinese Exclusion Act of 1882 and Hawaii. University of Washington Tacoma.

I'm probably forgetting some other source I looked at while typing this so I may have to edit to add it in later.

Footnotes:

1. I'm referencing the views of the time here, not speaking for myself.

2. Molly Maguires