All the logic being thrown around here is correct. These buses exist because the municipal governments of the Bay Area, as well as the state itself, has spent decades abdicating their responsibility to develop transportation infrastructure. There was no reasonable way tech giants like Google or Facebook could possibly hope to fix MUNI, Caltrain, etc, and so an exclusive (and inefficient) network of buses was the only solution. It still beats putting cars on the freeway.
The importance of the anti-Google-bus sentiment has to be read between the lines. The newfound tech wealth of the latest SF tech boom has not floated all boats. The techno-elites get richer while everyone else gets poorer. This goes beyond the typical frustrations about gentrification and demographic displacement - this is really just a highly localized version of what HN itself likes to complain about: the rich get richer, the poor get poorer.
The causes of this are complicated. The protesters are wrong in that tech workers are not the root cause of their misery. The tech workers are also wrong in that this isn't idle whining - this is the beacon around a very large social and political failure that pervades every minute or every day life in San Francisco.
cletus has a better explanation about why this whole thing is screwed up. He's also explained why I GTFO of SF and into NYC instead.