The former United skipper forced Alfe-Inge Haaland into premature retirement after injuring his knee in 2001 – something he later admitted was premeditated in his autobiography.
Speaking to ITV Sport, Keane said: "Many times I went on the pitch to hurt players, because that was my job.
"I went out on the pitch to hurt players, but never injure them. Plenty of times people would give me stick over my Irish background, call me an Irish so-and-so, you know all of that.
"It was all just stupid, heat of the moment stuff."
Keane won seven Premier League titles at United.