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Eich, donated to California's Proposition 8 campaign in 2008 which sought to ban gay marriage and his appointment has made many uncomfortable, including Mozilla employees.
Christie Koehler, head of education at the firm who is gay, wrote on her blog: "It's hard for me to think of a scenario where someone could donate to that campaign without feeling that queer folks are less deserving of basic rights."
Eich responded: "I am committed to ensuring that Mozilla is, and will remain, a place that includes and supports everyone, regardless of sexual orientation, gender identity, age, race, ethnicity, economic status, or religion."