boyfriend is on a dating app…

A friend of mine just sent me a screenshot of my boyfriends dating profile on facebook dating.. His profile mentions that he’s looking for something casual and to add his snapchat. He also wrote in his bio that he’s just looking for friends but on a dating site? I haven’t mentioned it to him yet bc I know when/if I do he’ll find a way to make it seem like it’s not a big deal and it feels like a big deal to me. I need others opinions on how to proceed…