The author is not an extreme libertarian. He is not even a consistent libertarian. These were private acts committed in the privacy of a home. They harmed noone other than the voluntary participants.
How many times have I heard libertarians here post that drug users ought to be able to kill themselves? They aren't hurting anyone else. So this idiot chose a slightly weirder, if no more perverse, means of killing himself. Libertarians wouldn't send John Belushi's dealer to the gas chamber. Why should they send this guy to jail.
The author just wants to impose his old fashioned conservative morality on other people. And I agree. Eating people is wrong.
It's nice to know that there are moral judgments that even self styled 'extreme' libertarians will make. This confirms my belief that deep inside every libertarian is a conservative waiting to get out. It's just a matter of where you draw the line. And once you start drawing lines, you aren't a libertarian--at least not in a consistent or pure sense.