Where I'm at is I think this:
If I use an LGPL library in my code and I find a bug and fix it
is a big if.
I would suspect that, for a majority of projects, the number of people who use the code and also will fix bugs in it is vanishingly small compared to the number who download and use the project.
Which is why I don't find his argument very compelling. He's making an argument for an edge case of users and generalizing it to all users. Even as a professional developer I can honestly say I've never fixed a bug in open source code I've downloaded.
In a sense, this is just an example of the stereotypical (and, of course, not universal, but many a joke and anecdote has been told here and elsewhere about it over the years) open source community myopia: Assuming everyone who uses their software is an interested developer with an abundance of free time. "You don't like something about my project's user interface? Why, just fork the project and change it to be the way you want! That's the beauty of open source!"
So, yeah. If you're an interested developer who is intimately familiar with the guts of an open source project and spends a large amount of time interacting with that project, it actually probably is in your rational self-interest to submit your bug fixes to the project. But that's a big if.