A lot of this goes back to eugencis and the falsified idea of skull shapes and measurements which they use to claim as a reliable way to deduce lineage, criminal behavior and intelligence. If you search for a 19th century book called “The races of the old world” by Charles Loring Brace you will see the justification for this
This is where my “Finnish” (although part of Russia at the time) ancestors were also not considered white due to the presence of an occipital bun on the skull which similar eugenicists associated with the neanderthal.
Eugenics is truly one of the ugliest eras of “science” and is a good reminder to step back and ensure that you are avoiding cognitive biases.
Now if we could just shake the scientific myth (yet a manufactured socioeconomic reality) of race which is just as flawed.
There are lots of books that document this by the way, a simple google search for “Simian features Irish” will return enough results from that period of history to quell any debate.
This obsession with “Simian features” is a major reason why it is “non-PC” to call people of color apes or monkeys, it was, and is actively used to categorize people into groups in a way which those of an “aryan” background could dehumanize them without guilt.
Here is a collection of images from the above google search that demonstrates this in relation to Irish people.
I wouldn’t necessarily attribute the anti-Syrian hysteria to the entire “right” - and many Arab Americans are steadfast conservatives. But there is a populist racism that is clearly inciting anti-Syrian sentiment; meanwhile the very similar influx of whiter Bosnian Muslims into the United States, particularly to St. Louis, receives very little attention.