Boyfriend made a joke about swapping partners with a new friend of mine. Is this a red flag?

I talked to my boyfriend of 1 month about meeting with a new friend and her boyfriend to go climbing next week. I suggested that he come too so I won't be the third wheel. He agreed and then said he could try taking away the bfs attention so that I can have girl on girl quality time with the new friend. And then he said "or maybe we can swap partners, kinda like swinging." It completely caught me off guard that he would even think about something like that. Am I in the wrong for being upset?

Boyfriend made a joke about swapping partners with a new friend of mine. Is this a red flag?
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