The Republican senator is seen as a possible 2024 US presidential candidate.
Tom Cotton shared his views on slavery in an interview with the Arkansas Democrat-Gazette.
He also attacked the New York Times 1619 Project’s effort to make slavery a focal point of American history for US schools during the interview.
The New York Times 1619 Project was launched last year to coincide with the 400th anniversary of the arrival of African slaves on America's shores.
It would place the consequences of slavery and the contributions of African-Americans at the center of US history.
Cotton wants to withhold federal tax money from an elementary and secondary school curriculum promoted by the project.
Criticism of Cotton's remark was swift.
"If chattel slavery — heritable, generational, permanent, race-based slavery where it was legal to rape, torture, and sell human beings for profit — were a 'necessary evil' as @TomCottonAR says, it's hard to imagine what cannot be justified if it is a means to an end," tweeted Nikole Hannah-Jones, a Pulitzer Prize-winning journalist who launched the 1619 Project.
Robert Reich, who was US Labor secretary under former President Bill Clinton, sought to tie Cotton's remarks to the 2020 election battle for control of the Senate.