There's a disconnect here. How does the absence of analytics mean the site continues to function with reduced usability? You could argue that over time the site's usability would not increase as much as it might be due to missing analytics data, but it won't be reduced just because the Google Analytics beacon isn't present on the page.

If you think that having analytics data is such a benefit to the user, explain to them why you want to track how they use your site and let them decide whether they're happy with that. That's all this law requires.