To an England-born person now making his home in Northern California (PG), some extreme American accents would also be "foreign". Indeed, in idiomatic English, "foreign" doesn't
necessarily mean "from another country" but can also mean "from another place/region" or even just "strange and unfamiliar".
(I'd bet a sensitive-enough analysis would show that even North American accents "foreign" to northern California have a very slight disadvantage in the bay area startup community. The tiniest of things can send signals of mutual-understanding and shared-goals, fairly or not.)
Focusing on the "non-United-States" sense of "foreign", in order to take offense here, is thus yet another example of why a shared, subtle, native-like understanding of the nuances of language is so important.
Appreciating the whole range of senses of "foreign" makes it easy to interpret the PG quote sympathetically, as being about practical comprehension. Focusing on just the primary sense of 'foreign', as if the word only meant "other-country-origin", leads to time wasted on misunderstandings and taking-offense.