Woltz was just a sicko who didn't want better looking men around to distract the little girls. He wanted to control Fontaine or make him submit... didn't you guys notice how Fontaine broke down in tears in front of the Godfather? He himself wasn't a killer, he was just an entertainer and Woltz didn't want to have to pay him any money or insurance benefits. We learn later in the novel that he had growth or some type of wart/cyst on his vocal chords and Woltz prob didn't want to have to pay for the diagnosis/surgery/etc.. and yeah Fontaine did make Woltz look ridiculous and I kinda wish they would have cut Woltz's balls off after the film was over...