The north in Westeros is xenophobic

Does Randyll Tarly hate the wildlings in the books?

Randyll Tarly has not been mentioned very heavily in the books, other than references Sam made, so little canonical information is available about him. However, we can based on what we do knowledge speculate.

We know he puts honor high on his list of priorities. He supported Aerys Targaryen, his rightful king, during Robert's rebellion and his liege lord Mace Tyrell during the War of the Five Kings.

He also did not want Sam to bring Horn Hill into his house as he considered him weak, as he was not good at fighting and could not have led his people into battle.

He also didn't want Sam to become Maester, although he was clearly very well suited for the role as he didn't want his son to serve other lords. Although he despises his son, he still sees his name being Tarly and wants him to do what he can to be proud of it.

Given that he's so proud of his name and honor, and only has the perception that wildlings are bad people and not part of Westeros (as most people in the Seven Kingdoms believe), it would be enough for him to form one very strong opinion of what is right and wrong with something that realistically he knows absolutely nothing about, simply because the entire empire sees them as an enemy.

He might also have been furious that not only had his eldest son broken his vow on the Night's Watch not to father children, he had the child with an enemy of the kingdoms, and if it was known it would bring him much shame and his Family.

Aegon

He only supported Aerys because Mace Tyrell did, which is implied because he later also followed Renly just because his liege lord Mace Tyrell did. If he'd taken care of Law, he would have been with Joff or Stannis. Was he really interested in laws?

Aegon

Sorry, but some other disagreement. He did not allow Sam to join the Citadel because "Tarlys do not wear chains or serve little masters". Also, Sam could return to Citadel without forging his chain and assert his rights as Oberyn Martell did. NW was just a way to make sure he wasn't causing Dickon any trouble. Not only did he kill Sam to spare his wife the pain, he didn't care about killing relatives when he made it clear to Sam. The correct word here would be "pride", not "honor".

Random832

If he becomes a maester, doesn't he still have to give up his last name? Maesters we meet seem to have only one name, and Aemon [Targaryen] implies it's their pre-maester first name.

Aegon

@ Random832 Being a maester takes years. Being a NW man only takes a few weeks. Oberyn Martell became a maester, but after a few years got bored and came back. Once you complete your chain and take vows after years of study, you will be disinherited. Otherwise, you can quit at any time. Randyll couldn't risk that.