Here's a best theory of uchiha lifestyles.....
Born, raised by sharingan user parents of which breed hatred of the nature revenge, learn some deadly skills, possess a little bit of sharingan abilities, starting to love, starting to understand, killed everyone, or trying to kill everybody.
In sasuke's case, please skip to the last one of the above statement. These clan can kills with or without reasons as suggested by the plot. But if they have good reasons to kill, they just overjoyed it.