It sounds like your grandparents were emotionally abusive, that can be even worse than physical abuse. If they used words and emotions to hurt others, then no they were not nice people. They may have done some kind and generous things for you, but they definitely were not nice.
Maybe I should have clarified. They were nice to everyone else. We have a very strong tendency to act normal around others, so I know they can be nice. As to the rest of the family (primarily my mother and myself), you are right, they are emotionally abusive. I don't think they even realize how dangerous their words are. I'm sure they wouldn't mean to say such things if they truly understood the impact of their words because I know they love us very much. I am very uncomfortable with myself right now because I feel I am making excuses for them and there isn't one. Period. Since I have not been able to make them understand my limits in this regard I try to limit my contact with them as much as possible and when I can't avoid them I limit the conversations to very banal subjects.

I just wrote out part of a long response giving advice on how you might handle similar situations, but I realized you weren't asking for advice. You have your own way of handling those situations and who is to say mine would be any better.
Claire, if you want to go ahead and write down any advice please feel free. It may be different from my own way of dealing, but it can't be any less valid, and we might learn something from it. In fact please do. I would love to learn how other people deal with abuse that doesn't come from family or lover.

Often we think of abusers in terms of people who are closer to us, but there are times when people instinctively seem to know how to hit your weak spot and will attack you, perhaps without even realizing that they are attacking you.
But what people don't always realize is maybe that one last cutting remark they made was the last straw that sends their waitress over the edge to committing suicide that she's been so busy thinking about that she's been giving them lousy service. Maybe she was just trying to cut you down to build herself up so she could hold on a bit longer.
Not really an excuse, but I've just never felt comfortable imagining that I could be the one who could have made a difference for someone and didn't just because I felt justified in being nasty back.