Down that road lies the argument that Google should be treated like a public utility. If the only mode of transport available were sponsored taxis, then people would be rightly demanding for the ability to pay for a car or use a government run public transit system.

There are other search engines that work just fine.

Do the other search engines work fine because you pay them directly, instead of them being ad-funded? Because that's the argument the GP was using.

Okay, assume the taxi rides are free. The taxi driver is now wasting your time taking you all across town just for a selfish kickback. Meanwhile, you value your time, presumably, so you're getting more and more annoyed as they do this. I don't see how removing the cost of taxi somehow makes this scenario acceptable. What am I missing?

A selfish kickback? Would you drive a taxi for free?

Nobody forced you in that free taxi, you got in on your own. Use another service if you don't like the cost of "free" (ads).

Yes, freedom of choice, et cetera. But what do you think? Is this a defensible, ethical behavior by the taxi driver or not? Is it by Google or not?