"I generally support the President on a lot of things — I'm famous for that, or whatever, infamous for that — but the fact is I don't think he's right on this one because I think people have addictive personalities and some people react to freedom differently than others and we better be ready for it because it's coming now," Matthews said on "Hardball."
Matthews had two members of the Kennedy clan, author and activist Christopher Lawford and former Congressman Patrick Kennedy, on the show to back him up.
Lawford said that the two most dangerous drugs — alcohol and tobacco — are already legal, so ending pot prohibition would only compound matters. Kennedy, meanwhile, argued that today's weed is much more potent than it was in Obama's "Choom Gang" days.
"I think dope, marijuana makes you sort of vague out, and sort of lose interest in tomorrow, two weeks from now, two months from now. Where ya headed? I do believe that," Matthews said.
Matthews joins a chorus of Baby Boomer pundits who have recently spoken out against marijuana legalization.
Tina Brown argued that legalization will make America "less able to compete with the Chinese," Joe Scarborough said that pot simply "makes you dumb" and David Brooks suggested that Colorado voters who helped marijuana prohibition in the state were "nurturing a moral ecology in which it is a bit harder to be the sort of person most of us want to be."