Encourages me to explore w girls but gets mad after?

My bf encourages me to do sexual things with one of our friends. Her bf feels the same way as mine does. Last night she said her bf didn’t wanna cuddle, well I was ready for bed and mine would be up for hours yet anyway so I invited her over to our place to cuddle and sleep by me, when I told my s/o that I invited her there to stay the night he got mad at me for it. He’s the one who always tells me to do things with her so I just don’t understand why he gets angry when I do.