I think it's both. The Malfoys are being invasive. On the other hand, in their view Harry is acting like a child who refuses to take care of himself because he thinks that will punish his parents. If he was eating and sleeping voluntarily, they wouldn't be as concerned and would be more content to wait at a distance for him to accept that they care. As it is, they feel they have to care for a member of their family and protect the one mediwizard who seems capable of healing Lucius.

Harry has been around people who mostly treated him as an adult for the last few years, so he finds being treated like a child insulting.

And thank you!