Personally I would leave it!! Wherever you go to work there will be someone who is talking drugs, being unfaithful to their wife/husband, breaking the law, drinking too much, etc etc the list goes on and on! (being a crap manager etc)
If we all declared what went on in the office I am sure half of the City of London would be banged up inside/thrown out of their homes.
So get on with it is my answer, and dont join in! People that **** things up or carry out certain activities sometimes get caught!