Skepticism

Someone claims that there is a glass of orange juice on a table behind a closed door.

The person making the claim complains that a skeptic will automatically reject the claim even though he has no justification for doing so.

My understanding is that skepticism is the rejection of a claim unless there is sufficient evidence to conclude that it is probably true. What constitutes sufficient evidence depends upon the claim. The degree of probability depends upon the strength of the evidence. 

As for the orange juice claim, one's word might be sufficient, assuming the individual making the claim is known to be a reasonably honest individual, because it's such a mundane claim. 

I know there are tables; I know there are glasses and I know there is orange juice so a glass of orange juice on a table behind a door that I can see is certainly reasonable assuming there isn't some reason to doubt the claim.

If the claim was that a pink unicorn was behind the door, since I'm not aware that pink unicorns exist, that would be a different kettle of fish. Now I would doubt the claim until I opened the door and checked.