Relationship issues

Recently, I got back together with this guy I used to date in middle school. It all happened really fast & it’s been great but I’ve noticed his friends say the n word and I’ve caught him saying it a few times now. Every single time I have called him out and I made it clear how I feel about non black people saying the n word & it just doesn’t seem like he gives a shit about it. We got into an argument & I just feel so confused. He isn’t arguing with me to say it but he’s like “it accidentally slipped” (idk how tf that happens) and says he won’t say it again but I want him to understand and believe and support what I believe in and support. Because well I don’t like racists. idk if I should leave him or what:/