Agreed; I'd also argue that web fonts shouldn't be blocked by default unless retrieval of them presents a privacy or tracking concern (unique source url, etc.).
In short, I don't disagree with what you've said at all. However, content providers must keep in mind that ultimately, they don't control how their content is presented or what part of it is displayed.
My issue is with the idea of grouping web font blocking with ad blocking. A user should choose separately if they'd like to block:
• Ads
• Tracking scripts
• Creative assets that may slow web performance (like web fonts)
• Other non-essential, non-creative scripts that may slow web performance