Other guy wrapping his arms around me in public?

(Precursor: if you have a problem with swinging, just click away now). 
Okay so my husband and I have been seeing this couple, mainly just for sex.  We hadn't really intended it to go beyond sex and friendship.  Anyways, the last time we hung out we went to a fair the next day with them, and suddenly the other guy was wrapping his arms around me in public and being innapropriately PDA-ish.  It made me and my husband feel uncomfortable, and I want to keep that just in the bedroom!  How do I address this without potentially hurting feelings?  I feel weird asking him not to hug me in public but then saying he can do whatever he wants in the bedroom?