You may think that an external cab company (or Lyft) should be able to come into SF and complete with local firms but you also apparently agree it is illegal. I personally consider it equally morally illegitimate for individual actors in a society governed by the rule of law to decide which laws and regulations "work" for them and which ones don't, then to disregard those they don't like. And in practical terms I think it is irresponsible for a group of people with one goal -to make money- to set up a company which they know is breaking the law, and to convince a lot of people to join them in breaking the law (their drivers) and creating ridiculous contortions that allow them to pretend not to be governed by the rules ("the donation thing" e.g.) when everyone knows they are a taxi service, plain and simple.
In practice these behave exactly like a taxi service. I don't think it matters much who owns the cars. No one would argue that a cab company from, say, LA, should be able to just bring a portion of its fleet to SF and start picking up passengers without complying with the laws that govern taxis here. If these start-ups affect the market in essentially the same way, we and they all know they are trying to enter a market with rules in a way that does not abide by them