It's a parody of US Federally funded anti-drug commercials;

"This is the joint that Joe smoked"
"This is the friend that sold the joint that Joe smoked"
"This is the dealer that supplied the pot in the joint that joe smoked"
,etc, etc....until;
"This is the terrorist that...."

, basically telling teenagers that if they smoke a joint, then they are responsible for terrorist acts carried out in the US.

Some people don't like taxpayers money being used for such messages, even if they are anti-drug, and even if there may be some basis for it. Especially when the US government is doing Jacks hit to lower the foreign oil consumption, which involves $ figures of a huge magnitude larger than the pot $ figure, and could be shown to have just as much likelihood of supporting terrorism.

The ad was designed to grab attention, and that it did.