This sentence makes me cry. We can split this sentence up into:
It's worth it to consider the historical roots of democracy in India
People don't often take it (the historical roots of democracy in India) into consideration in arguments (as in, 'debate' or any attempt to make a point about the roots of democracy or democracy itself.)
People think that Indian democracy is ONLY because of the British influence, and no other interesting factors.
Taken together, the author is saying that the roots of democracy in India was caused by many more factors than simply the British influence (since the British colonized India and are a democratic nation). The author encourages looking into these extra factors so that people are aware of them when discussing democracy in India.