It is because those structures of domination are indeed legible that we need not spend so much time hand-wringing over the status of uttering "I am Trayvon Martin." In fact, doing so is part of a very disturbing personalization and psychologization of politics in the wake of post-modernism. This is what keeps us dwelling anxiously over whether identifying with Trayvon exculpates us or only make us guiltier. Keeps us focused on noting whether white privilege and white supremacy subjugate us or work for our own benefit. Keeps us vacillating between effacing all difference and constantly upholding it.
The problem with these kinds of vacillations is that they completely erase the most important political concept there is: solidarity. Solidarity is not based on sameness of racial identity or of lived experience. Nor is it a kind of sympathy that reaches across difference. Instead, solidarity is just a sheer determination to struggle together. It is a commitment to work collectively to overturn the structures and institutions of racism, in the recognition that, while white supremacy may not victimize us all, it is only yet another instrument of arbitrary division and domination, and to pretend that one person cannot be motivated to action by the injustices visited upon another plays directly into its hands.