Someone being unhelpful is one thing, hindering is another.
A person being unhelpful doesn't necessarily intend to be unhelpful. It may well be innocent and unintentional.
When someone is hindering – not only being unhelpful but also getting in the way – that is something else. It pays to have your guard up.
If you're confused between the two, always look at someone's intention. Not just the surface intention with what they say – look at their actions and what they actually do. That will tell you all you need to know about intention.