I totally agree, it depends what everyone is sacrificing by one parent giving up their income.
I sit at home because DH likes the endless baking I (obsessively 
) do, I think he feels a bit more like he's the man/provider which he likes and that he doesn't have to think about anything other than his job Mon-Fri. We like the dynamic, and what I could be earning were I working would make no difference to the lifestyle the household has. For me, it's super leisurely.
If I was sitting at home, super leisurely, doing all those things I enjoyed whilst my lack of income meant DH needed a second job, or that we had to make cutbacks that detrimentally affected the whole household, then yes, I'd view myself as lazy, and I wouldn't find someone pointing that out, judgey. It annoys me when sahms pretend that something detrimentally affects the household is out of the question to fix, when the fix requires them to get a job.
The poster above who is a single mum working full time, is a perfect example. No excuses, just getting on. She's still an excellent mother. I'm absolutely sure our children don't feel any more or less loved because she holds down a full time job and I don't. Except she does everything I do, plus work full time. I have a lot more admiration for her, than I do for me. I'm not a worse mother. I do however, have a far lazier lifestyle, as do many, many sahms. I just wish they'd own up to it instead of pretending it's not. Obviously there are exceptions.