Can I ask my coworker stop using gay slurs?
What's your reason for asking him to stop using slurs?
I found out I don't get offended about it anymore.
It's not acceptable for a person to use gay slurs, especially when it is a coworker at work since there is an expectation of professionalism. Even if you aren't personally offended by what he says, others people can be and they will suffer emotionally from hearing those slurs. You are absolutely right in wanting your coworker to stop using slurs and if he doesn't abide your request you should talk to people in management and Human Resources about what is going on.
I'm going to yell at my coworker and call him a homophobe.
It is good to speak up against bigotry. You may try taking to your coworker calmly as there is no need to yell.