When Noah and his family were off the ark, God made them a promise that he would never again flood the earth no matter HOW evil humanity became. So to ensure that all of humanity remembered his promise, God gave us a ‘Token’ (gift). The purpose of this token was to remind us of his promise whenever we see the rain fall upon the earth and that gift was the Rainbow. (Genesis 9:12-17)
Therefore when we see Thousands of homosexuals marching in the streets with the Rainbow as their flag, they are essentially implying that they are proud of their sexual immorality whether God likes it or not while simultaneously reminding God of the contract that he made with humanity never to flood the earth again.
But whether they realize it or not the masses who gather together to celebrate their sexual immorality, and those who carry these colorful flags are essentially provoking God to wrath in their Ignorance.