On September 28, 1868, a mob of Democrats massacred nearly 300 African-American Republicans in Opelousas, Louisiana. The savagery began when racist Democrats attacked a newspaper editor, a white Republican and schoolteacher for ex-slaves. Several African-Americans rushed to the assistance of their friend, and in response, Democrats went on a “Negro hunt,” killing every African-American (all of whom were Republicans) in the area they could find. (Via Grand Old Partisan)

On April 20, 1871 the Republicans passed the anti-Ku Klux Klan Act outlawing Democratic terrorist groups.
The Miller Center reported:

On April 20, 1871, at the urging of President Ulysses Grant, Congress passed the Ku Klux Klan Act. Also known as the third Enforcement Act, the bill was a controversial expansion of federal authority designed to give the federal government additional power to protect voters. The act established penalties in the form of fines and jail time for attempts to deprive citizens of equal protection under the laws and gave the President the authority to use federal troops and suspend the writ of habeas corpus in ensuring that civil rights were upheld.

Founded as a fraternal organization by Confederate veterans in Pulaski, Tennessee, in 1866, the Ku Klux Klan soon became a paramilitary group devoted to the overthrow of Republican governments in the South and the reassertion of white supremacy. Through murder, kidnapping, and violent intimidation, Klansmen sought to secure Democratic victories in elections by attacking black voters and, less frequently, white Republican leaders.

In related news – Republicans led the charge on civil rights and women’s rights.

http://www.thegatewaypundit.com/2014/04/this-day-in-history-republicans-pass-anti-kkk-act-outlawing-democratic-terrorist-groups/