The reason he didn't turn it down is because that bong he's holding is worth a small fortune.
Michael Phelps Caught Smoking, Apologizes
Michael Phelps will do just about anything to look cool at a party. After winning 14 Olympic Gold medals, the only thing left on his plate was to pick up a bong and go for the high score.
“I engaged in behavior which was regrettable and demonstrated bad judgment. I’m 23 years old and despite the successes I’ve had in the pool, I acted in a youthful and inappropriate way, not in a manner people have come to expect from me. For this, I am sorry. I promise my fans and the public it will not happen again.”
“He arrived with a group of girls hanging all over him. Jaws hit the floor when he walked in. You don’t get many celebrities in Columbia, so when Phelps comes to your party it’s a very big deal.
“He didn’t know many people so you’d think he’d be a little shy. But he was loud, obnoxious and slamming beers from the get-go.
“Every girl wanted a piece of him and every guy wanted to be his best buddy. He couldn’t get enough of all the attention.”
As he basked in his hero status, Phelps knocked back beers and shots of spirits. And when a student offered him the glass bong engraved with red writing, he did not hesitate, says our source. (source)