To answer this question, we first have to examine what Aristotle means by “virtue.” For Aristotle, virtue is the means between extremes. It is the middle way between excess (too much) and deficiency (too little). For example, Aristotle labels generosity as a virtue and shows that it is the mean between wastefulness and stinginess. Generosity takes the middle way of giving just enough to other people without giving too much and wasting resources or giving too little and becoming a selfish miser.
The question, then, becomes whether Aristotle would view Socrates's action of proclaiming human wisdom to be “worthless” as a mean between excess and deficiency. Socrates's position actually seems quite extreme. After being told by the oracle at Delphi that “no one is wiser” than he, Socrates decides that his true wisdom comes from knowing that his wisdom is worthless, that he actually knows nothing. Socrates concludes that this does indeed make him wiser than many who have an inflated opinion of their own wisdom and knowledge and end up deceiving themselves.
While he might appreciate Socrates's reasoning, Aristotle would probably decide that his action of spreading the message of the “worthlessness” of human wisdom falls outside the mean. Socrates's proclamation, Aristotle might say, may well be viewed as less than truthful by many people who do not understand it. His speech is less than straightforward and frank, and it lacks intelligibility and may even fall into the deficiency of mock modesty. Therefore, Aristotle would likely say that Socrates is being unvirtuous in his declaration.