Social justice movements have generally increased social freedom over time, and it is for this reason that they have generally been popular. This is why most people support things like gay marriage and abortion rights, even if they are not personally affected by it. If social justice now takes a turn towards less freedom (which is what a 'systems of oppression' view would do in terms of speech and expression), it would become much less popular. The reactionary right could start winning big again. Therefore, the goals of social justice need to be geared towards freedom, not just harm prevention.