Her mum was in the hospital on a ward with dementia patients. He basically went off on her about looking after herself, pointed round the ward and was saying if you don't want to end up like this, drink water, eat 3 meals a day, blah, blah, blah. You have to remember he's a condescending twat and it's with his condescending tone. He basically spoke to her like shit (if we're going by how the story was told, which I'm sure is accurare). Not only speaking to her mum like that but also, not nice him speaking like that with a room full of other patients and possibly their families. Disrespectful either way. I'm sure R's mum knows what she needs to do, but if there was any empathy there, they would help her. Getting older also means forgetting things and that can sometimes mean eating. They can't be present for their own kids, so I doubt they'll do the same for her mum.
I can also imagine J thinking because his mum is doing 'OK' , her mum should too, but everyone is different. I could go on but it's infuriating.