Agreed, unless of course Quirrell realizes it is a possible interpretation, at which point he either throws members of the family or their corpses or the tapestry into an airship and manipulates Harry into shredding it. For added effect, he names said airship "The World", then feels much less terrified. (Until Harry applies the principals behind said magical airship to create a magical mech capable of destroying planets, of course!) The defense professor's relationship with puns, however, seems insufficient for him to attempt such a strategy. (Then again, he figured out an interpretation of Harry's ritual chant at the end of Self Actualization...)