What made Mark hate the steamboatman in Life on the Mississippi? Why do you think Mark still wanted to talk like him despite this hatred?

In Mark Twain's memoir Life on the Mississippi, it is clear that Twain had a love-hate sentiment for steamboat captain Mr. Bixby. It was Twain's boyhood dream to learn how to pilot a steamboat on the Mississippi River. He sought out Mr. Bixby as a teacher, who was known as one of the most renowned steamboat pilots of his time.
Twain admired Bixby for his skill and was grateful to learn from such a skilled instructor. However, the captain often directed intense verbal abuse at Twain as he struggled with the challenges of riverboat piloting. Steamboat workers were notorious for their profane language, but even so, Mr. Bixby was particularly awful, according to Twain's memoir.
The job was tougher than Twain expected, and several times Mr. Bixby woke him in the middle of the night to instruct him. However, Twain was more resentful of this aspect of the job specifically and did not take it personally. I would describe Twain's negative sentiment toward Bixby as dislike, rather than hatred. He likely wanted to speak and act like Bixby in order to fit in with the man and his crew.
For more insight into your questions, including quotations featured in Twain's memoir, refer to my answer for a relevant question linked below: