Officially, it can be 'valid' but not 'sound'. As all of the Lewis Carroll logic exercises involving flying pigs and boiling oceans attest, logic has nothing to do with reality per se. Validity, the primary property logic pursues in an argument, preserves truth, but some source outside logic needs to fill in the truth-values of the source premises.
Many authors introduce the separate notion of a 'sound' argument which is one that is both valid and 'grounded in reality'. Of course, at that point they have departed from logic in its strictest sense because logic cannot tell you how to verify your axioms.
And, as to the example, yes, deducing anything from a contradiction is always a valid argument. If your premises contradict one another, logic can't help you, and you need to address your sources of information, instead.