Every prophet was given enemies who rejected the Truth and opposed it through all the means they had.
One of those means was through wrongfully branding the people of the Truth with evil names to try to scare other people from following them. [It should be noted that the names Ahl-us-Sunnah have given the innovators, are because they do indeed engage in the innovations. So Ahl-us-Sunnah do this justly, to warn the muslims from innovation and it's people].
Hence the Prophet (sallallaahu alayhi wasallam) and his Companions faced this from the Mushrik-s - see (3):186.
They called him a magician, madman, fortune-teller, liar etc.
And similarly, the people of Knowledge and Truth have also faced this from the Innovators who wrongfully branded names of defamation and mockery onto them.
Some did so out of ignorance, thinking themselves to be upon the Truth. Others did so maliciously, to repel people from the Truth, even though they knew it to be the Truth.
25.1 THE JAHMEEYAH
- call Ahl-us-Sunnah "Mushabbihah" claiming that affirming the Attributes according to the most apparent meaning, is Tashbeeh.
25.2 THE RAAFIDHEE SHEE'AH
- call Ahl-us-Sunnah "Naasibee", i.e. adversaries of 'Alee, because they befriend Aboo Bakr and 'Umar. Hence the Shee'ah claim that anyone who befriends these two has automatically declared enmity for 'Alee and the Ahl-ul Bayt!!!
25.3 THE QADAREEYAH
- call Ahl-us-Sunnah "Mujabbirah" claiming that affirming Allaah's Decree implies that the slaves are forced upon the actions they do!!!
25.4 THE MURJI-AH
- call Ahl-us-Sunnah "Shukkaak" - the Doubters, as they say "I am a Believer if Allaah has Willed," while the Murji-ah forbid this saying and insist on only saying "I am a Believer," for they claim that to add "if Allaah has Willed," shows doubt in having Eemaan. [See 26.4.1].
25.5 THE PEOPLE OF LOGIC AND KALAAM
- call Ahl-us-Sunnah "Hashaweeyah" [people with no worth] and "Nawaabit" [weeds] and "Ghuthaa" [scum], as they think that any one who's not upon their logic and theology are unintelligent rabble. However the truth is that their way is not needed by an intelligent man, nor is it useful to a stupid man.