Answer:
There could be so many deeper meanings one can realise in this quote. Depth itself is subject to so many subjectivities of one's experiences, imaginations, natures and nurtures, and much more.
The deeper meanings of this quote could be that perhaps living and death are not ends of a spectrum, where one is the beginning and one is an end. Perhaps then, if death is not opposite to mere living, then mere living is not equivalent to life. Parrado seems to be saying that what gives life to life is love, and the absence of it is death. Love is what gives meaning to life, and perhaps, can be equated to it.
Parrado opens up the quote to universal implications by denying that "courage or faith or human will" could be the opposite of death.
The quote says that "Love is our only weapon." It could perhaps be the only thing with which we can survive; survive and fight. Love then not only gives meaning, but also the strength, the power, and the means to live, like a weapon can.
And "how does anyone miss that?" Sometimes, it is rather difficult to recognise love, because of the multitude of its forms and manifestations. But irrespective of that, it seems to be present where life is, or death isn't.
