Chelsea fought back from two goals down to draw 2-2 and force a quarter-final replay.
The Spaniard claimed that he waited to shake hands with the Scot, but Ferguson walked past him without completing the usual formalities.
After the game, Benitez said: "I was waiting at the beginning. It's up to him, I was in the way waiting.
"Ask him - if you are brave enough ask him. It was his decision. I was ready and waiting.
"I have some education because I know a lot of people are watching, so I know what I have to do."
United and Chelsea will now meet in a replay at Stamford Bridge to decide who will face Manchester City in the semi-final at Wembley.