Whenever people say stuff like this, I wast to bring up the idea of the "net good" of the implementation.
Twillio doing this doesn't take away from the tragedy and it's not preying on vulnerable people. It's helping people through their service. If they get press for it, so be it.
It's unfortunate that people think that in order for one party to "win", another party has to "lose." I think this is a good case of win/win.
Or, use Gmail to make unlimited domestic calls. Its disturbing that companies are looking to get marketing even out of tragic events like these.