The analogy doesn't work because pollution is an actual negative externality, there's demonstrable harm being done and if they're not paying fines (or fines are too low), they are reaping disproportionate benefits from it.
On the other hand, I can only see positive externalities from Uber.
Preliminarily, note that whether you characterize an externality as negative or positive is a value-laden judgment. One of our power-company-apologists might well say the same thing if they had a certain moral/political outlook.
And if you literally can't think of any negative externalities that Uber generates, I submit that you haven't approached the problem dispassionately. As people have repeatedly pointed out, there are concerns about Uber's liability insurance (even now that it offers its own limited coverage -- externality: uncompensated, injured people), policy concerns about surge pricing (externality: people can't afford to get where they're going at peak usage times), policy concerns that Uber drivers are free to turn down passengers (externality: possible discrimination), concerns that decrentalization makes it more difficult to ensure that vehicles are safe for passengers (externality: possible injuries), concerns that decentralization makes it more difficult to ensure that drivers have safe driving records and clean criminal histories (externality: possible crime against passengers more possible injuries), difficulty verifying that drivers are actually covered by the insurance that they (and Uber) claim covers them in the absence of formal licensing (externality: uncompensated injuries). These are just off the top of my head. Maybe you don't find all of these these persuasive, and maybe you think that the benefits of Uber outweigh all of these (I happen to agree!).
And, to be clear, I think that Uber is doing much (MUCH) less harm than most serial polluters by ignoring the relevant regulations. The point, though, is just that Uber isn't the first company to take the attitude that it is free to ignore the law. It's just the first one I can think of that is also popular.
> You seem to be very confused about the rest of the stuff so I'm not going to bother addressing it.
I really wish you would, since that's the substance of the comment, and I'm pretty sure I'm not actually confused -- though perhaps you disagree. (Note that your disagreeing, and my being "very confused" are not actually the same thing.) And you should do a little more thinking about what constitutes a "negative" externality -- sometimes it is clear that it constitutes a cognizable economic "cost," but other cases are no so clear cut.
Here is some recommended reading: http://repository.law.umich.edu/cgi/viewcontent.cgi?article=... Especially page 911. The point is not just that a value judgment is necessary to determine whether something is a cost or benefit (though sometimes it is) but also that a value judgment is needed to determine whether a would-be externality is the sort of thing that a person or entity should be expected to internalize.
On the other hand, I can only see positive externalities from Uber.