The original comment didn't say it was worth less - they said it wasn't real work at all. If someone's willing to pay you for it then it's real work.

So saying it pays less is irrelevant. It's not a competition to see how can look down on whom.

And it's not just Instagram. They said that the MacBook Air wasn't suitable for work, and just gave Instagram as one example of what it is suitable for. I could do my job (programming language research) on a MacBook Air. I know someone who writes medical text books on a MacBook Air. Are these things not real work?

I don't know why the author couldn't just say 'A MacBook Air wouldn't be suitable for my work'? Why add the extra snide bit that if you could then you aren't doing real work? Why communicate that idea at all, directly or indirectly?