Chick-Fil-A has been notoriously anti-gay for over a decade, publicly donating millions of dollars to anti-LGBTQ groups and opposing same-same marriage.
Despite claiming they turned over a new leaf in 2012, stating they will no longer donate to organizations that promote discrimination against LGBTQ people, there has been significant evidence to the contrary. In 2015, they gave one million dollars to the Fellowship of Christian Athletes, a religious organization with "a strict 'sexual purity' policy, prohibiting any 'homosexual acts.'" This was just one donation among many other anti-LGBTQ groups.
This is why the CEO of Twitter came under fire for tweeting that he ate at a Chick-fil-A, and during pride month no less.