Why is he being so childish about this?

I have been talking to this guy for months now. We get along well. We understand each other and we both have an understanding of what it is we have going on with each other. We’re two people experiencing/ dating one another and if things get taken to the next level then it just does. I’m a single mom. I have a son so that way works best for me. We have/do have sex and we’re safe about it. We haven’t had many problems up until yesterday. I had a self care day recently. I got my nails did and I told him about it. He asked if he could see a picture of my nails but he didn’t want a normal picture, he wanted a more fun picture. He wanted me to take a picture of me grabbing my bare boob. The idea of it did seem cool and fun to do. I had taken the picture and told him I would send it but then I actually thought again before sending it and decided not to. My reason for not sending it was because when it comes to sending private pictures like that no matter how much you trust a guy, a picture is forever and you don’t know what could happen and how you can get exposed. I have a son to think about and I don’t want any pictures of me like that floating around for the sake of me and my son. That was the exact reason I gave him and he wasn’t mad but he was childish about me not sending it. Saying things like he could alway get someone else to send a picture like that but he preferred it to me. He told me I should have never took the picture if I wasn’t gonna send it and that he was gonna stop asking me to do things for him. He started to be very hostile toward me and that actually bothered me because it’s literally just a picture and outside of choosing not to send that I have done plenty of things for him that he asked of me. Things that I was comfortable with but the moment I have one small boundary, he says he’s not upset but he decides to treat me differently.

Why is he being so childish about this?
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