If I want a bit of clip art for a presentation or stock image for a website, is it disdainful to say it's irrelevant to me if it was made by a living human or a computer?

I want the thing. An artist getting paid is a means to an end for this purpose. To you and others, the artist getting paid might be the end. That's fine for you, but I may not have reason to care.

There is not some universal right to get paid for things you like to do. Pay is a transaction between someone who wants something and someone who can provide it. I once saw a Ted Talk by a busker who was a mime or something and was calling what they do "work" (and was complaining about people who didn't respect that). I found it ridiculous because effectively they are a beggar, they are doing what they want to do and hoping someone gives them money, and in some cases, feeling entitled to it. I think it's this perception of entitlement (real or imagined) that rubs people the wrong way about artists, at least ones complaining about not getting paid. If you want someone to give you money, do something people want. The universe doesn't owe you a business model.

Along the same lines, weavers and scribes and travel agents and a million other professions have moved on. Automating low value art is not any different, nobody owes you anything.

It's not disdain for artists. It's the notion that artists' works are inherently valuable or worthy of a 'living wage'.

They are unfortunately not, nor is anyone's labor inherently valuable.

It’s like the disdain for servers complaining about tips. It’s not part of the bill so it rubs people the wrong way because it feels entitled.