Except they're really not. They accessed data from an API that is only available to the Lyft app by creating some fake profiles. That means their profiles couldn't legally have agreed to the app's terms and conditions, so it wasn't legally permissible for them to access the API. So no, they weren't just accessing information that Lyft were "sharing publicly".
They said that was really a program to deal with people violating their terms of service. So one would think, given Uber's demonstrated commitment to enforcing its own terms, they'd have the utmost respect for competitors' terms. Of course, if they violate competitors' terms to gain an advantage, then we know where they really stand and what their own standards are (i.e., no standards other than "anything that gets us ahead is good").
I don't think determining legality and harm should be a boolean operation. There are layers of subtly and nuance in most things, and the law is one of them. I don't think posting the F word on a forum where the owner doesn't want you to post it should be treated as an equal violation of the law as deliberately abusing your competition as a billion dollar business. The amount of damage, and perhaps potential damage should be considered. When I swear a reasonable person would think the harm is minimal. When I try to sabotage another company where the damage could result in billions of dollars of lost investment and thousands of jobs vanishing a reasonable person would think that's pretty bad. They're technically the same 'crime', but they're obviously not the same in scale.
In this particular case, Uber is guilty of breaching Lyft ToS's clause around no data mining. However, this seems like an insignificant infraction, there is likely to be zero legal penalty. Lyft's only recourse is to either shut down Uber's accounts or feed them bogus data.
Yes, T&C are the legal terms and conditions under which you have permission to use an app; violating them ought, geenrally, to be illegal, provided they are valid in form and process.
> Isn't that the same as using the F word on a forum when you agreed not to?
Yes, breaking that agreement could also be illegal. Why is that relevant?
> Didn't we go through all this with Aaron Swartz and one or two other high profile hackers?
Whether a thing should be illegal is a broader question than whether it should be criminal, which is a broader question than whether it should be covered under a particular criminal statute with particular penalties or pursued in a particular manner by prosecutors.