Do you need to visit Italy to write "The Merchant of Venice"?

One of the more famous twentieth-century theories of non-Stratfordian authorship of the works of Shakespeare holds that Edward de Vere, the 17th Earl of Oxford and one-time protege of Queen Elizabeth the First, wrote the works instead.

One part of that controversy that may be well suited for the discussion of contradictions is the claim that the frequent setting of Shakespeare's plays in Italy is an indication of a travelled man that had visited that region. Founder of the Oxfordian theory, J. Thomas Looney, wrote:

[The author of the Merchant of Venice, RCK] knew Italy first hand and was touched with the life and the spirit of the country. 

(Wikipedia notes that this claim had also been used to support the authorship candidacy of the Earl of Rutland and the Earl of Darby, who had also travelled the European continent.)

Oxfordian William Farina refers to Shakespeare's apparent knowledge of the Jewish ghetto, Venetian architecture and laws in The Merchant of Venice, especially the city's 'notorious Alien Statute'. 

There is evidence that De Vere lived in and traveled in Italy for over a year. He was there when writing to Lord Burghley Sept 24, 1575, though he disparages Italy and "care not ever to see it anymore" in that letter. De Vere departed Venice in March of 1576. The Venetian Inquisition received testimony of De Vere's fluency in Italian. Oxfordian Anderson argues that Oxford

... visited Venice, Padua, Milan, Genoa, Palermo, Florence, Siena and Naples, and probably passed through Messina, Mantua and Verona, all cities used as settings in Shakespeare.

In contra-indication, Shakespearian scholars have pointed out:

• As far as The Merchant of Venice is concerned, "the play itself knows nothing about the Venetian ghetto; we get no sense of a legally separate region of Venice where Shylock must dwell" (Kenneth Gross)
• Similarly, the setting is described as "a nonrealistic Venice" and the laws invoked by Portia as part of the "imaginary world of the play" inconsistent with then-existing legal practice (Scott McCrea)
• The Alien Statute bears little resemblance to any Italian Law (Charles Ross). 
• Lewes Lewknor's 1599 English translation of Gasparo Contarini's The Commonwealth and Government of Venice provides details on Venice's laws and customs that Shakespeare could have used in Othello, for example.
• The Italian scholar John Florio, who lived in England and was consulted by Ben Johnson for Italian details for Volpone, published two books, First Fruits (1578) and Second Fruits (1591), the latter a bilingual introduction to Italian Language and and culture, which have been suggested as the origin of Italian idioms and dialogue (e.g. in The Taming of the Shrew) by Kier Elam and Jason Lawrence.