Do I have the right to be upset?

Yesterday, my boyfriend and I went out to eat, and he started telling me that this girl (who he knows likes him and was going to ask him out, despite the fact that I am dating him) messaged him on Facebook. He offered to show me the messages, so I said sure. When we got back home, I asked him if I could see the messages since he had offered, and he said no. I got up to get myself something in the kitchen, where his iPad was laying on the counter, but I had NO intentions on getting it to look at his messages. He jumps up off the couch and grabs his iPad, yelling at me, thinking I was going to get his iPad to read his messages. He then deletes the messages with the girl. This really upset me because it made it look very suspicious like he had something to hide. He says he just didn't want me to read the long messages, but he had offered, and now I feel like there was something he didn't want me to see. Am I wrong to be upset?

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