Answer by taking a quote from the following article:

Carroll was born in Joliet, Illinois on May 18, 1945. His father worked in a coal processing plant. The family moved to San Diego in 1954 where Carroll grew up. He describes his early years in Ocean Beach as an ideal childhood.

Carroll did not believe in an omnipotent, omniscient, omnipresent god. However, in his essay "Why I am not an atheist", Carroll described his dislike of the term "atheist" because he feels that the term is being exploited by theists and used as a straw man argument. He felt that the term implies a dogmatic set of beliefs and carries its own share of negative baggage. So, Carroll suggested that atheists might as well adopt the term "Brights" with all its negative connotations.  The only religion that Carroll found attractive after abandoning Catholicism, despite never following it, is Buddhism as taught by the Dalai Lama.  Carroll has always maintained the opinion that people have to be more skeptical of religion than they are now. He said in multiple interviews that religion is an area that skeptics don't target enough, and that pure faith is winning the race against critical thinking.  Carroll tended to have a moderate outlook on religion. He believed that religion has a role to play in people's lives and he didn't condemn religion for terrorism. When asked about the relationship between violence and religion he said that he can't recall anything negative about his religious upbringing, and that maybe Catholicism can provide more good than harm. He didn't believe religion causes wars, he rather believed that it serves as an excuse for people who will go to war regardless of religion's existence. Carroll believed that some people rely on religion as their only source of morality and as a source of comfort. However, he found it distressing that some people are unable to find meaning in their lives without religion. In an interview with Beyond a Doubt he said  "There is nothing dull about a life without fairies, Easter bunnies, devils, ghosts, magic crystals, etc. Life is only boring to boring people."

Why did he dislike that term?
" because he feels that the term is being exploited by theists and used as a straw man argument. He felt that the term implies a dogmatic set of beliefs