How can you claim that a true dharma practitioner has a conscience independent of the dharma?
Meaning, they should not mistake their particular relative and conditioned views as representing THE Dharma, which is an eternal truth.
The Dharma is not some objective thing independent of the world; it is a collection of truths, ideas, practices and values all of which are expressive of the way one is and ought to be in the world. In this sense, it is always and already political.
Ok, well, in this case we do not agree. Dharma is two-fold, the Dharma of realization and the Dharma of texts. What is the Dharma of realization? It is pretty straight-forward, summed up in the Lalitavistara, it is blissful, free from proliferation, luminous, permanent, etc. The Dharma of texts allows one to taste and realize that state.
Buddhist history clearly shows this; as do numerous nikayas and shastras.
Buddhists have acted politically, but politics and Dharma are not the same thing, and historically, political śastras are considered "mi chos", i.e. human ethics. That is different than "lha chose" i.e. Dharma.
Nagarjuna did not see any contradiction between the dharma and giving robust normative political advice. Nor did the Buddha.
Secular ethics and the teachings of realization are compartmentalized in the Indo-Tibetan tradition. That of course does not mean that the canon does not record Buddha's runins with kings and ministers, but what is remarkable is that in his advice to them the goals of realization always are prioritized over and against any secular value his advice could have had.