What people are referring to in that regard is how, in 2011, Brendan Eich (who later founded Brave Software) stepped down as CEO of Mozilla, 11 days after his appointment to said position, after it came out he had donated $1000 dollars to the campaign for California Proposition 8 in 2008, a proposed state constitutional amendment seeking to ban same-sex marriage. Prop 8 wound up passing, although it was overturned a few years after the fact in court.

Here's an article from when Eich stepped down about the whole ordeal.