I always considered my friend to be a kind and caring person so why is he ending our friendship over something so petty ?

We are both single and attractive people in our 30’s. Im 

recently single after being married for 7 years and I thought I would become friends with benefits with this guy in an attempt to detach from my ex husband. Also I want more sexual experience since I’ve only ever had my husband as my sex partner. Im not looking for a relationship and he’s not looking for one either. But he said the next woman he gets with he wants to be his wife. I’ve known him for a very long time I mean since we were 19. We had dated casually back in college nothing serious though. He was talking about how we both have grown and matured since then. So we agreed to just satisfy each other sexually since we are both single. He was very respectful towards me during sex and asked me what I felt comfortable doing and he told me I didn’t have to do anything I didn’t feel comfortable with. He was asking me what sorts of things Turn me on the most. When we go to do the act I discover his package is tiny he can’t even put it in me it’s that small. didn’t expect to him to have a tiny package. So I said don’t we don’t have to have sex because it’s not going to work out if he can’t even put it in. He said we can try a different position and I was like I don’t think any poSition is gonna work. I told him I needed to be honest with him and I don’t want to hurt his feelings but he is very small.. I mean the size of my thumb. I’ve never experienced that before my ex husband was 10 inches and I was caught off guard.