Google around: https://www.google.com/search?q=marijuana+lung+cancer
He simply pointed out that it's an anecdote.
Another fruitful Google search: https://www.google.com/search?q=ld50+marijuana
Technology and science enhances everything by default. The exceptions are rare, and weed will not be one.
It's not the method, it's the toxicity of the chemical itself. As others have mentioned, regardless of the method of extraction, purification, or intake, this does not change the ridiculous amount that would have to be pumped into the blood in order to kill someone.
Cannabinoids do not affect the brain stem, the primitive part of the brain that controls respiration and the heart. Many other drug overdoses are affected through this avenue. Cannabis does not and cannot.
You would have to adulterate it with another drug, in which case, it is a different discussion.
This isn't a discussion about how far "pure weed" can get you, it's about what's going to happen now that the laws don't deter people from applying technology and science to weed, and whether a 'fatal dose' is just a limitation of the literally stone-age techniques we currently use to consume stone-age quantities of weed in its basic plant form.
We know that technology, along with research, have proven very beneficial for devising better drugs, better ways to consume drugs, and better ways to produce drugs.
We know that already the concept of rolling up dead flowers to smoke has been superseded by vaporizers delivering 5 - 10 times more potency without all the smoke.
We know that weed has been excluded from even basic studies, leaving much to be explored and much to learn. Alongside the studies that have not been done lies innovations and technological and scientific enhancements that have not been invented yet.
There is no reason to assume we can only ever consume very tiny volumes of weed with fire, like our ancestors 700 generations ago.
Physiologically, you would lose motor function long before you were able to kill yourself. So maybe in 2056 if somebody produces a machine that lets you take in 50kg of THC in a single hit, don't use it.
[1]: http://druglibrary.org/schaffer/library/mj_overdose.htm
With THC, you'll be more likely to reach a threshold of total discomfort and/or unconsciousness before you reach the fatal dose.
It's self correcting like Mushrooms. You can take an insane amount, but there is a good chance you'll be transported to the center of hell for several hours and never ever want to go back.