Supporters of same-sex marriage have long argued that their foes were irrational because allowing gay and lesbian couples to wed had no impact on straight couples. Thanks to research published June 11 in the Public Library of Science, supporters of same-sex marriage now have empirical proof to back up that claim.

“[A] deleterious effect on rates of state rates of opposite sex marriage has been argued to be a motivating factor for both the withholding and the elimination of existing rights of same sex couples to marry by policy makers — including presiding justices of current litigation over same sex couples rights to legally marry,” Alexis Dinno and Chelsea Whitney of Portland State University wrote in their study.

More: Study: Same-Sex Marriage Has No Effect on Opposite-Sex Marriage Rates

It’s funny that anyone would need a scientific study to prove this but hey… there it is.