The point seems to be that the web is cool and hip, which attracts people without computer science backgrounds. Without a solid footing in software design fundamentals, "hack it until it works" seems like a perfectly valid way to run a development cycle.

The desktop is not cool or hip, so the people doing it tend to be people who really want to be there, not chasing trends. It's a vast oversimplification of the situation, sure.

I think a fair number of us non-cs-ers end up in web development primarily because html/css is more accessible. I, myself, was more interested in design than coding, and I only learned the basics as a means to creating the designs I wanted. From there you might start learning some JavaScript, you might start learning some frameworks (like Backbone, or ember), and you might get fairly proficient with them... but I don't think the web attracts non cs people because it's "cool" or "hip".

I don't know about anyone else, but I learned almost nothing about software design when getting my computer science degree.

CS degrees are not a catch-all. Most teach data structures, algorithms, a little AI and database theory. Few teach how to structure programs.

I'm pretty sick of the "I work with people without CS degrees" excuse. Good software design really comes down to experience, persistence, and taste.

Necessary but not sufficient. I've worked with a lot of very experienced, very persistent people, and I'm sure they even had good taste, but they were shitty coders. In fact, their persistence was a requirement for them to be able to get their jobs done at all, given how bad they were.