Question: Is Sanatana Dharma Sectarian?
Answer: It Is Pure Sectarian-less Religion
Dharma literally means "intrinsic nature." And sanatana means "eternal." So sanatana dharma is the eternal intrinsic nature of something. For example the sanatana dharma of water is liquidity and the sanatana dharma of chili peppers is hotness. So what is the sanatana dharma of the living being? His sanatana dharma is service. Everyone has the propensity to serve. Therefore people serve their nation, their community, their family, etc. And if they can find no one to serve, they will get a dog so that they can serve the dog. The perfection of such serving propensity is to serve the root cause of all existence, i.e. to serve God. Just as by watering the root of a tree all the leaves and branches are nourished, by serving God we are able to perfectly serve everyone. So this serving God is the real sanatana dharma. This can be executed by anyone in any religious tradition. A Hindu can do it. A Muslim, a Christian, a Jew. It does not matter how one may be designated externally. If he is purely serving God without any ulterior motives, he has become perfectly situated in sanatana dharma.
So sanatana dharma is not another sect of religion. It is the pure essence of religion when religion becomes completely free from all material designations and material motives.