Spock's father was Sarek, and he was full Vulcan and a master of his emotions. He found it logical to marry Amanda, Spock's human mother. Only later in life (in TNG) did you see Sarek lose control of his emotions during his last and fatal illness, Bendii Syndrome.
http://memory-alpha.wikia.com/wiki/Bendii_Syndrome
Spock fought for control of his emotions because he was half-human. When he was young, he was bullied by other young vulcans because he was known to be half human, half vulcan, making him the target of racial bigotry.
We forget that Vulcans still have emotions and an emotional makeup, their history was one of savagery and war. Only through the study and training of logic do they achieve Kolinahr, the purging of all emotions, and the mental discipline of logic. Not all Vulcans in history believed or followed that, and many offshoots left Vulcan to pursue their own ideas - notably the Romulans who are believed to be Vulcan in original origin.
http://memory-alpha.wikia.com/wiki/Vulcan
Yes, I am a nerd and Star Trek geek. And proud of it. My only regret is not being able to attend the 50th anniversary Celebration in Las Vegas this week.