It is debateable if Shakespeare was an anti-semite. His defense of Jews (Shylock’s famous “If you prick us do we not bleed? If you tickle us do we not laugh?….” speech) is regarded by some as a deliberate attack on anti-Semitism. It should be noted that at the the typical mode of accomodating religious minorities in England usually involved somewhat gruesome methods of capital punishment. It is unlikely Shakespeare ever met a Jew, and few in his audience had (Jews were banned from England in the period, though a few were there pretending to be from Spain something we know since when arrested for being Catholics they go off by convincing the court they were really Jews and really weren’t loyal to the king of Spain), though there were large Jewish communities in Europe. It’s hard to make a clear conclusion as to his biases – indeed some people question whether he even existed at all.
Mark Twain is well known for having denounced discrimination against Blacks (and Jews), and was a prominent contributor to African American causes.