Flat rate vs multiple rates

In India, the situation of people is such that if we charge simple food and clothes at 18 per cent, there will be serious repercussions

Prime Minister Modi has made a strong case against a flat rate of tax in GST. Flat rate vs multiple rate has been a raging controversy all along. There are supporters on both sides. Some countries do have flat rates like Australia, Cambodia, Chile, Denmark, Israel, Japan, South Korea, Nepal, New Zealand, Taiwan, and many African countries. But we notice that these countries are not having so much disparate strata of people and are also not federation. Inequality of income is not so rife in these countries. 

Now let me give you some countries with different rates. Belgium — 21,6,12. Brazil