You are forgetting British divide and rule policy. Prior to 1857 there was no significant intercommunal violence in India.
What I am about to say, please accept that it comes from a respectful approach.
I have heard the above quoted lame excuse so many times it has become childishly redundant. I cannot believe it keeps getting repeated without fair analysis.
We are criminally guilty of viewing history through a modern prism, that surely cannot be right, it amounts to spreading lies.
Gays were illegal, the meaning of gay was to be happy, in the 19th century conference was held to discuss if women can be considered as human, no language on earth is the same as it was just couple of hundred years ago, women and man have only received equal rights less then a century ago , Switzerland gave women the right to vote just in 1971.
The point being that society and societies were different, societies change due to evolution, education, exposure to other cultures or religions or any number of other factors, the region of India that you and everyone keeps assessing by giving the above statement was a different region. The Marathas killed nearly half a million Biharis and Bengalis in the decade before the battle of Plassey, they did not kill Indians, they killed the other, the other being the Bengali and Behari.
People had different lives, anywhere there are different communities, there will always be problems and I'm sure they existed then, but those problems were limited to extreme localities. How often did anyone leave their village? people accepted the other and accepted the differences. Right now everyone is hell bent on appearing to be alike, in that effort the minority gets absorbed, and if the minority is catered for in any and shape or form, the majority feels aggrieved. you cannot win. The best way is to accept the differences and move on.
There are various factors that have accentuated the differences and identities, they include greater mobility with access to roads and railways, greater literacy, especially higher education and many other factors.
These have allowed each community to see there are others like them, and intermingle with them more often and at a deeper level, that process carry's with it influence and development of societal identity, an identity that's individual to your unique set of believes and values.
I could go on but the point is made, before the British, these things were not so obvious because our societal makeup was different, the mass education did not exist, the railways did not exist, the higher education structures did not exist. The more educated you are, the more clearly you are able to express yourself, and define your own identity that is individual to yourself, an identity that defines you and protects your interest according to your own terms.
If you want to go back to living in the villages, without the access to mass transportation, and what modern society has delivered over the past 200 hundreds years, living in villages that were clearly defined as Hindu village, Sikh village, Muslim village. When people did not eat or drink from the same utensils if another religious group used them, then yes, you are right, these problem will disappear.
Please, be my guest.