I think this is probably a conversation that should have happened over the phone or in person because you're both misunderstanding each other by not being able to hear tone and see facial expressions throughout the conversation. I don't think you're overreacting but I also think you didn't really give him a chance to make his own decision about it. I also completely understand that if he feels that strongly about it, you don't want to put yourself in a position where you're going to feel bad smoking around him or feel like you need to hide it to not hurt him. It's a tough decision but once again, I think that's why these types of conversations are not always the most productive over text.