We know this because we see both late medieval legislation and extrajudicial violence directed at "aliens: including Jews (bef. 1290 and converts after), Welsh, Scots, "Flemings," Italians, "Germans," even English "northerners," not to mention Normans and general French, etc.
Comments
"The land exhausts us by demanding payments, and the people’s disgust is heard/While we are silent and wait for the light." (trans. Susan Einbinder)