I couldn't find anything from laymen citizens, but according to Arthur M. Schlesinger's book, Robert Kennedy and His Times, certain prominent news publications believed he was unqualified due to his lack of experience.
"If Robert Kennedy," the New York Times noted sarcastically, "was one of the outstanding lawyers of the country, a preeminent legal philosopher, a noted prosecutor or legal officer at Federal or State level, the situation would have been different. But his experience...is surely insufficient to warrant his his present appointment.
Robert Novak of the WSJ said that RFK could be an "unqualified disaster" if appointed.
Alexander M. Bickel of the New Republic said that "Mr. Kennedy has demonstrated specific grounds of disqualification....On the record, Robert F. Kennedy is not fit for the office."
In the Senate Judiciary Committee, there were some grumbles of opposition, again due to inexperience. According to Page 234, Richard Russell, Senator from GA, believed that "it's a disgrace for a kid who's never practiced law to be appointed..." according to LBJ, who agreed with him.
However, it's important to recognize where the Senators were coming from. They were Southern Democrats who, according to RFK, had "difficulty in the South to vote for any Attorney General," likely due to the ideological differences between Southern Dems and Northeastern Dems (where JFK and RFK were from) at the time.
As for nepotism, The Nation reportedly blasted RFK's appointment as "the greatest example of nepotism this land has ever seen".
Starting on Page 229, you can read more implicit warnings of nepotism.
Even RFK himself was concerned about the appearance of it.
John and Robert kennedy had talked in Hyannis Port immediately after the election. "He asked me if I wanted to be Attorney General. I said I didn't want to be Attorney General....In the first place, I thought nepotism was a problem."
But overall, once the confirmation hearings started, the criticism died down and RFK went through it fairly smoothly.
As a follow up question can anyone shed any light on the anti-nepotism laws that were passed after the Kennedy administration. I'm sure I heard that had happened but when I tried to research it I couldn't find any information about it.
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