Would you get mad at the person your significant other is flirting with?

So yesterday we had this volunteer come in and as soon I met him we just hit it off like we knew each other for a long time. Joking, teasing at each other, even flirting. I would catch him staring at me, at times he would quickly look away or if not it's like he wouldn't even care that I caught him staring at me. At times he would find a way to like touch my hand or back. Which I didn't mind at all. So today he decided to tease me again, by wearing his favorite team jersey ( a team I don't like and he knew that's why he wore it ) so I told him how his jersey made him look ugly and he said how the hairstyle I did yesterday made me look ugly. Once again the teasing/flirting continued. So everyone is witnessing all of this, they also saw how he ran to his car to give me his sweater because it started down pouring rain all of a sudden. So we both started giggling when he was telling me how good I look with his hoodie on , so I said, I'm glad you think so because now I'm going to keep it. He started laughing and said something while walking away. So all of a sudden the girls that I work with was like attacking me saying like, "omg I can't believe you're doing this, I didn't expect it from you". So I'm like so confused, and luckily my co worker that I became best friends with told me that he was married and I honestly didn't know. I was being completely honest with everyone about what I was told. So one of the girls was saying how she would yell and cuss me out if she saw me wearing her guy hoodie, because that's something you don't do at all. Which I do understand but I just feel like if that person didn't know I can't get mad. But I will get mad at my significant other for doing it.

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Even my boss chimed in because she thought it was odd for him to do it especially since he barley knew me and just let me put it on
Would you get mad at the person your significant other is flirting with?
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