This character likely doesn't fit in your game
As others have already said, you need to have a "Session 0" using the Same Page Tool -- in this session people do not play or roll their characters, but instead discuss what do they expect from the game, what do they want to play, what is OK for them and what is not OK.
Playing without a good understanding what do you want to play is like inviting everyone to "play cards", while some of you mean "play Black Jack" and some mean "play poker".
If your Druid player wants to be such a peaceful guy, probably it will turn out that this peaceful guy doesn't fit in the group, and he will have to roll a new character. Probably you will find a way to play together. Probably other characters will catch up and reroll themselves instead, also becoming Druids and joining your "problem player" on his journey. Probably you will understand that you just don't want to play together because you expect too different things.
Just understand (and tell it to your players) that any outcome is OK. No one should play a game that is not enjoyed. If you can make a game enjoyable for everyone, so let it be. If you can't, so let it be too.
Just discuss things. Just talk to each other. It really helps.
P.S. Ah, it is also possible that when you suggest your players to discuss "a problem with that Druid char", they will respond with "What problem?" -- perhaps they are just totally OK with his behaviour. Or not OK, but ready to handle it in-character. Again, everything is possible.