Moderate and conservative Republicans of the civil war era regarded the Radical Republicans as villains, and particularly dangerous ones. Some even suspected that Stanton was involved in Lincoln’s assassination.
So-called Radical Republicans drove and passed the 13th (1865), 14th (1868) and 15th (1870) Amendments, and tried to impeach Eastern Tennessee Democrat President Andrew Johnson (1868) because, basically, he was thought way too lenient on former Confederates.
Curious that most of our radical pro-Confederates these days consider Johnson just another Northern devil.
Many people say that somehow Lincoln would have been more forgiving than Johnson, had he lived.
Regardless, that period from Appomattox in April 1865 until the presidential election of 1876 is pretty murky and misunderstood.
Certainly I'm no expert on it, and am disinclined to defend one particular group or another.