It's not just that some people include A into lost sales though, although that is the major problem. Some people are strongly against group A because they feel that they should not get whatever they pirated for free. You'll see this a lot in conjunction with the word "entitled". I can understand their point, too.
Personally, I think the world is a better and richer place for more shared culture (see also group C, who likely exists largely because of A), and if that means people who weren't going to pay anyway freeload through piracy, so be it. If the would not convert to a sale, then they should essentially be ignored. The piracy that should be focused on is B, because that's the only one that actually has a real monetary effect.
Personally, I think the world is a better and richer place for more shared culture (see also group C, who likely exists largely because of A), and if that means people who weren't going to pay anyway freeload through piracy, so be it. If the would not convert to a sale, then they should essentially be ignored. The piracy that should be focused on is B, because that's the only one that actually has a real monetary effect.