My boyfriend decided suddenly he wants to be a vegetarian/vegan

My boyfriend watched a single documentary and has decided he wants to become a vegetarian and cut out as much cheese as possible (only have it on a cheat day). One of our favorite things to do together is go out for dinner, try new things, and share stuff so we can try more stuff on the menu. I also LOVE to cook, but him turning to a plant-based diet rules out a lot of stuff. I’m down to cut back and eat healthy and make better choices, but now I feel like I’m in this weird place where if I suggest we eat something unhealthy (like pizza) I’m being judged and if I cook him something that isn’t in his new diet he won’t eat it or be upset that I’m

not supporting this new choice. Has anyone else gone through this? Just need some advice, because every time he mentions it I immediately get mad and that obviously isn’t working...