Why is he so insecure?

A stock image of a girl having the exact bikini
A stock image of a girl having the exact bikini

My husband (28) and I (25) were at the beach yesterday in Sardinia, and I was wearing this exact bikini (One of my favourites for years, even before I met him) when he noticed some random guy apparently having a raging bulge. He pulled me aside to ask if he was staring. I said he did once or twice, and I held his hands and walked a bit further than that guy. He literally wanted me to go back, but I insisted on choosing a spot further away. He appeared so pissed off, and told me how he didn't like that guy having a bulge. It wasn't under my control, and according to him, me showing off my hot figure (acc. to him) caused this. I reassured him and was in a problem-solving mindset, but he ain't ready to understand. Have any of you faced a similar situation? How do I deal with him?

Why is he so insecure?
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