Do you, as the website operator, have the right to copy and serve these fonts to your visitors? (Actual question; my guess is that you don't according to Google Fonts, but could be wrong.)
> proxy the request through your own servers
Isn't this worse? Assume that your visitor does not want Google contacted at all as part of their visit; isn't, then, the potential leak of an IP address simply a side effect? The website is still leaking timing of when a visitor accessed the site, potentially their usage patterns...
Personally, I think this is a bit of an absurd argument... I think, at most, consent should be enough for third party requests. I was mostly responding to GP's claim that the user can't reasonably consent to such use.