The core of Gruber's argument is that Apple's market share (not Google's) is growing quickly, whereas Microsoft's is falling.
Gruber also acknowledges that the numbers don't take into account the whole of the PC market, and he brings up a couple of important points you need to consider before thinking that Microsoft is making up for its losses in the sub-$1000 PC market. Quotes:
"What is particularly alarming about Microsoft’s numbers is that revenue from its Windows PC division suffered an even greater year-over-year revenue decline than the company as a whole: 29 percent."
"Even given that NPD’s numbers represent only retail sales, is there any reasonable doubt that Apple’s share of the non-retail market for $1,000+ computers is also growing?"
Also, it's misleading for you to suggest that Gruber implies that Microsoft is "completely F-ing it up" when comparing them to Google. His 'working title' aside, the purpose of the comparison was to demonstrate that other companies in the industry are not falling short of projections, as Microsoft has. He is suggesting that blaming the revenue decline on the economy isn't a strong argument.
You use the term 'propaganda' pretty loosely. Many things written on Daring Fireball are sarcastic and overly-dismissive when it comes to Microsoft, but it's clear that John Gruber put a lot of thought and work into this essay. Try to do the same with your criticism.