For the record, according to the introduction to my copy of The Crucible, by Christopher Bigsby, (play by Arthur Miller), "In 1692 nineteen men and women and two dogs were convicted and hanged for witchcraft [in Salem, Massachusetts]."
Comparing nineteen deaths to six million is just silly.
There are other reasons why this comparison is half-baked. As stated by others, the Holocaust was genocide (before the term existed!), and the Salem witch trials were specific targeting of individuals. The Holocaust had no regard for the individual, whereas the Salem witch trials were based upon it, whether fairly or not.