>>Alex63+sF
The quote is frequently used by fanatics (those who look at democracy with a religious fervor), as a conversation ender -- particularly when used after criticism of some democratic process. It almost always implies "we cannot discuss the shortcomings of this system because it is the best". It also often has an implication of "this is the final word on democracy, it is defined as the best, therefore whatever you come up with cannot be as good". This second association is why I replied as I did in my original comment -- it is the same as "love it or leave it".
tl;dr: the quote itself isn't bad, it just has been coopted by those with a certain fanatic mindest.