First thing off the bat:
Those familiar with Shaw may know that this IS a quote pertaining to eugenics, which Shaw WAS--as were many in his day--a proponent of.
THIS IS NOT MEANT TO BE A DISCUSSION OF EUGENICS.
At least not on the whole...at some point it may enter in, but this is not the FOCUS.
Second, this is a quote often taken out of context for negative effect, so to clarify--Shaw WAS talking about eugenics and DID make mention of an idea which should seel altogether ghastly in this day and age, namely, "a humane gas" which would put down those who COULDN'T justify their existence.
Obviously in this post-Holocaust world this isn't very PC-sounding and, indeed, is probably the darkest mark on what is otherwise an almost unparalleled writing career.
However, what is OFTEN mistaken about the quote--and as is the case with a popular YouTube video featuring it in a Glenn Beck special--is that Shaw was using this idea as a call to Hitler and Stalion and a call for ETHNIC cleansing, which was not the case; Shaw lived in a time when it was believed that the world would very soon be far too overpopulated--and to the man's credit he DID have a point about that, didn't he?--and so many were calling for eugenics as either a way of creating "better" human beings via selective breeding or later genetic manipulation--ie, taking Nietzsche's Ubermensch idea literally and trying to come up with a race of Superman a la Captain Kirk's nemesis Khan, for those otehr Trek fans out there--OR, as Shaw meant and stated here, though getting rid of those who, as he put it, "aren't pulling their weight."
Shaw would have gassed those who were, say, drug addicts or those who commit a murder or who have twenty-one children and never go looking for work.
It DOESN'T make Shaw's comment any more right, it's still a bad idea to gas peoiple like that, but he DIDN'T approve of ethnic cleansing OR Hitler--he was actually notorious for very Leftist ideas, so Beck's saying he sympathized with Hitler and his dieas is really not only a stretch but an outright lie, if ANYTHING Shaw might have leaned more towards a very libertarian set of ideals, but I digress, as if Beck has actually READ Shaw--and he wasn't targeting ethnicities and, most important of all, it was a convention of the time...we respect George Washington and the man had slaves, which we would see today as apalling, but again, it was just part of the times.
That being cleared up, onto the real topic at hand...