I don't agree with this comment in this context, but I do know for a fact that the Washington DC Metro does not extend to the popular Georgetown shopping and nightlife district for precisely this reason.
That's the same reason Atlanta's MARTA doesn't extend into Cobb County. I don't think it has much to do with intercity rail, though; it seems to be mainly an issue with opposition to metropolitan-area rapid-transit systems, with people worried that they'll blur boundaries between nice and not-nice neighborhoods within the same city.
It's not what you don't know that hurts you, it's what you know that isn't so that does. That is a canard, often repeated but without basis in fact.