Why does he still want to be friends with me?

I was seeing a guy for a while and I found out he was married and confronted him about it as soon as I discovered he was married. He still wants to be friends with me though and I said to him I don’t think your wife will be okay with that and he said she wouldn’t but he decides who is friends with. He also said we are just friends and nothing more. Why does he still want to be friends with me? Isn’t that disrespectful to his wife?