Policies are not decided by shouting, they are decided by debates in our parliament.
And political parties support the affirmative actions because they know the ground realities. They know because they have to interact with them, to get votes for getting the power.
Although the upper caste politicians may not be personally in favour of reservations, for remaining in power his party has to continue with the policy. For they have to go the same people again for the votes.
The so-called "elite" class of India is ignorant as is fed with prejudice since the birth. All of economy is under the command of upper caste people. The government jobs and college seats reserved for Dalits only make them a servant. All the wealth and land was unfairly grabbed since ages. There are no enterprenuers in India because they are killed and suppressed by the family owned businesses, who hold on to the wealth by all unfair means. They don't value talent, but the lineage. And this inscestous inbreeding leads under-utilization of the human talent. No wonder, India fares so poorly in all the competitions as only a fraction of population is used to pick our representatives from.