I don't think the parent is arguing that taxes shouldn't pay for buses, but rather that the taxes that pay for it shouldn't be the targeted taxes like the gas tax, instead the money to subsidize the buses should come from the general fund, and the subsidy level should be something that people get to have a say in through the election process.
That's something I can get behind, for the simple reason that using the gas tax to subsidize buses is unsustainable: if it's working correctly it encourages drivers to switch to buses, carpool, and use more efficient vehicles (which is, in fact, one of the desired goals - get cars off the streets to reduce traffic and smog), but that means that the burden is now spread over fewer car-miles, so the tax needs to increase, driving more drivers to buses, until everyone is on the buses and where does the money come from again?