The forever problem of racism

Racism is nothing new but a perennial tension that exists as cycles of immigrants assimilate and they transition from foreigner to indigenous population. Yesterday's foreigner is today's native. Here's two examples: 

Evil May Day is the name of a riot which took place in 1517 as a protest against foreigners living in London.

The Gordon Riots of 1780 began as an anti-Catholic protest in London against the Papists Act of 1778, which intended to reduce official discrimination against British Catholics. The protest evolved into riots and looting.