It is a sign of the convenant God made with Noah

To not destroy the earth by flood ever again.

Genisis Chapter 9: 8-17

8. Then God said to Noah and to his sons with him:

9. “I now establish my covenant with you and with your descendants after you

10. and with every living creature that was with you—the birds, the livestock and all the wild animals, all those that came out of the ark with you—every living creature on earth.

11. I establish my covenant with you: Never again will all life be destroyed by the waters of a flood; never again will there be a flood to destroy the earth.”

12. And God said, “This is the sign of the covenant I am making between me and you and every living creature with you, a covenant for all generations to come:

13. I have set my rainbow in the clouds, and it will be the sign of the covenant between me and the earth.

14. Whenever I bring clouds over the earth and the rainbow appears in the clouds,

15. I will remember my covenant between me and you and all living creatures of every kind. Never again will the waters become a flood to destroy all life.

16. Whenever the rainbow appears in the clouds, I will see it and remember the everlasting covenant between God and all living creatures of every kind on the earth.”

17. So God said to Noah, “This is the sign of the covenant I have established between me and all life on the earth.”

Without Knowledge The Rainbow Was Hijacked

Interesting Enough, Back In The Late Seventies An Artist Decided There Needed To Be A Symbol To Represent A Cause. So, With All It's Beautiful Colors Filling The Sky, The Rainbow Seemed Just The Right Emblem To Fulfill That Fix.

Then He Was Urged By A Government Official To Make That Symbol To Fit That Mission.

First Of All, The Rainbow Has Nothing To Do With Any One Particular Identity or Ideology. Secondly, As This Movement Has Grown And Continues To Grow To This Day And Age, They Certainly Must Have Heard Preachers Explaining What The Rainbow Really Stands For. Thirdly, This Is Rebellion Towards God. It Is A Direct Spit In The Face To The One Who Created The Rainbow, Man And Woman.