In an article published in The Players Tribune on Thursday, Ramsdale said his commitment was driven by the desire to ensure that his brother, who is gay, can attend matches without fear of facing abuse or discrimination.
"Football is for everyone. If you disagree, maybe you're the one who needs to shut up and look in the mirror," the Arsenal keeper wrote.
"I want this game I love to be a safe and welcoming place for everyone. I want my brother, Ollie — or anyone of any sexuality, race or religion — to come to games without having to fear abuse."
England's Football Association launched investigations into several alleged incidents of homophobic chanting last season.
Wolverhampton Wanderers were recently fined 100,000 pounds ($127,000) for homophobic chanting by a section of their supporters during a Premier League match against Chelsea.
"Over the years, I've probably bit my tongue a few too many times whenever I hear homophobic comments or stupid things being said," Ramsdale said.
"I think maybe my brother has done the same, thinking it would make my life easier. All that ends today."
Ramsdale, an England international, played all 38 Premier League matches for Arsenal last season and helped them finish as runners-up to Manchester City.
