bf’s weird fetish? wtf?

last night he told me he wanted to watch me have sex with another guy and i’m super confused and i don’t understand why. i love him not any other guy so why would i want to have sex with someone else?? he says it’s hard to explain and he himself doesn’t really understand why he likes it so much. so what do i do?? i’m very confused so if anyone’s SO has asked the same thing or if you’ve done this before lmk what it was like and maybe why you did or didn’t enjoy it just so i can try and get an understanding for what my bf is feeling and make a decision from there oh also what do you guys think i should do and what would you do if you were me