I am white. I think the issue for many is that racism feels like a far-off, distant thing. We know the history of our country and, for some of us, that our ancestors had slaves or somehow supported or participated in racist institutions. We may know our grandparents are racist. We know it exists in this country still today (well, most of us -- those that pay even a modicum of attention to others). But it has never affected us directly. And if we've grown up in predominantly white areas, which much of the northeast is, we may not have witnessed it at all.
So it doesn't seem quite "real" to a lot of white people. We know it exists but we haven't seen it playing out because we're not tuned to it. We take for granted the way the world works for us and don't see the way it harms others. It's only really by spending time with people of color and, more importantly, listening to them that I think we can begin to see the way institutions and power structures and what are, to us, everyday interactions are stacked against people of color.
It's a tough awakening that a white person has to care a lot to even confront. It doesn't surprise me that the folks you spoke to, OP, got defensive, because confronting truths of racism means questioning things that we have always assumed to be one way. A white person might think, well, I studied a lot in high school and so I made my way into a good college. I worked hard in college so I have a good career. My race has nothing to do with it. When they're confronted with the truth that their race means they were likely afforded opportunities people of color did not have or that they otherwise implicity benefited from their privilege, they feel that their accomplishments are suddenly called into question. They hear someone saying that they didn't work hard to get what they have, not that other people have to work ten times harder to get the same thing.
That's just my observation as a white person at least. There are of course a lot of outright garbage racist white people who just hate people of color, but I hope your friends aren't like that OP.