>> Is Starbucks Free WiFi actually run by Starbucks or is it a malicious router placed in the same vicinity?

Both. The Starbuck Free WiFi is also a malicious router. All routers should be seen as malicious. That threat model is why we have secure websites. That's why VPNs are always a good idea, or Tor if you are really worried. But even then, those routers too must be deemed untrustworthy. At no point should one ever trust middlemen, be them routers or used car salesmen.