Habermas and insistence on the ultimacy of internal critique

“[The] call for self criticism, let us say, a self critical defense of the, achievements of Western modernity that signals both openness and a willingness to learn and above all overcomes the idiotic equation of democratic order and liberal society with unbridled capitalism. One the one hand, we must make it clear stand against fundamentalism, including Christian and Jewish fundamentalism, and, on the other, we must acknowledge that fundamentalism is the child of disruptive process of modernization in which the aberrations of our colonial history and failures of decolonization played a decisive role. We can at any rate make clear against such fundamentalist fixations that justified criticism of the West derives its standards from the West’s own 200 year old discourse of self criticism.”

full here

I wonder why Habermas insists that the West be judged according to its own standards only?? Why can't we have an external critique of the West?