Well, what he said is: 1) he does not like pro-marijuana lobbyists/activists ("bastards" as he calls them), 2) all of the pro-lobbyists (from his times) are Jewish, 3) he does not know why is there such a connection, 4) he provides a crappy explanation (psychiatrists? really?). Now I have no idea whether or not 2) is true (probably not), but correlations between ethnicity and lifestyle preferences can and do exist. Take Chinese approach to parenting - clearly different.
To sum up, the only thing that could possibly be offensive is either 2) or the overall tone of the fragment. Hence my question: is it because it's plain false? Or is it because such language is always xenophobic, regardless of available evidence?