In order to better address incidents of online violence resulting from uncontrolled public opinion in the era of self-media, network platforms are involved in decision-making during the early stages of online violence opinion formation. This can effectively prevent the formation of online violence opinions. Firstly, based on the inducement behaviors of online violence and considering the internal self-purification effects among platforms, self-media, and netizens, the costs and benefits of their autonomous behaviors during the initial stages of online violence opinion formation were defined. Next, a "platform-self-media-netizen" three-party evolutionary game model was constructed, and the behaviors of each subject and their evolutionary stable strategies were analyzed. Finally, numerical simulation experiments were conducted using MATLAB to verify the accuracy of the model and evolutionary results. To further reveal the factors influencing the cooperation among these parties, the impact of their initial cooperation willingness and related parameters on the system was explored. Simulation results show that a strong regulatory strategy adopted by network platforms, with clear guidance, can effectively enhance the cooperation willingness of self-media and netizens, effectively curbing the formation of online violence opinions.