תנא נעמן גר תושב היה נבוזראדן גר צדק היה מבני בניו של המן למדו תורה בבני ברק מבני בניו של סיסרא למדו תינוקות בירושלים מבני בניו של סנחריב למדו תורה ברבים מאן אינון שמעיה ואבטליון
Translation: Nemen was a righteous gentile, Nevuzradan (who personally took part in murdering tens of thousands of jews) became a righteous jewish convert. Some of the grandchildren of Haman (who tried to murder the entire jewish people) converted and learned Torah to in Bnei Brak. Among the descendents of Sisra (who wanted to destroy the jewish people in the time of the Judges) taught Torah to children in Jerusalem. From the descendents of Sancheriv (the Assyrian king who murdered hundreds of thousands of jews and sent us into exile) were some who taught Torah to the masses, and who were they? Shamaya and Avtalyon. (those were 2 of the greatest leaders of the jewish people during the time of the second temple, and the teachers of Hillel the Elder. Converts descended from one of the biggest enemies of the jews.)
The source? Tractate Gittin, a volume of the Babylonian Talmud, and a universally accepted text in traditional jewish literature. For those converts or prospective converts who are worried about being accepted in the jewish community because of your family's past, or even for your own past, don't worry. You won't be the first, and I'm sure you won't be the last. Even if you yourself are now an avid antisemite, if you come to me in the future and they are honestly looking to convert and live your life as a jew, you will always have a place at my shabbos table.