"I don't think anyone here is claiming that there is a *duty* to provide assistance. 'Duty' and 'obligation' are distinct concepts, and it is possible to have obligations without having duties.""Duty" and "obligation" are "distinct concepts"? Really? Let's see what Dictionary.com says:
du⋅tyOr perhaps the OED:
1. something that one is expected or required to do by moral or legal obligation.
dutyClearly a hugely important "conceptual" distinction!
1. a moral or legal obligation.