The rainbow is a biblical sign from God. When He reduced the population of the planet to eight people (Noah's family - him, his wife, his three sons and their wives) after the flood, He produced the first ever rainbow as a promise that He would never again flood the entire earth.

Just like June was traditionally the month for weddings and for many decades, women wanted to be a "June bride," the gay group co-opted things that were good and pure for their own evil agenda.