Survival of the fittest. It makes sense. I get the feeling that most of us are liars. We don't do it on purpose though, and I said most, not all. Its just that we aren't aware of the contingencies upon which our love and compassion hinges.
Imagine telling your family members, "I love you, but only so long as you do this or that". That doesn't sound like love, but then again, nothing sounds like love to me anyways. Love is more of an action because its all too easy to simply say the words and for them to be empty.
You make some good points there.
Let's look at 'love' first.
The strongest variety is said to be maternal love for offspring. It is touching to see a mare care for her new born foal. A bitch licking her pups, a tired Mum exhausted but proud, feeding her baby.
But I have seen this love wither and die in the case of some ( not all) mothers of profoundly autistic children. It is not always absolute, more conditional, as you say. The nature of autism sadly breaks the feedback loop of mothering. In extreme cases the child avoids eye-contact, protests when touched or soothed. This pattern will sometimes reduce the mother to desperate instrumental behaviour in return. Love cannot thrive here, other than as a most abstruse rarefied concept. Love has to have some reciprocity in the real world.
Let's take another, even more horrible example. Cannibalism.
I'm guessing that the well adjusted and kind users of these boards could never imagine being reduced to eating another human. But this has happened widely in the cases of complete famine. There is a pattern, a grim continuum, of descent into the unimaginable. (Data here comes from, Cormac O'Garda, Joe Lee, John Post, Sorokin, Gareth Jones, wiki and other sources)
The hungry first try to move to new sources of food.
If they are prevented from moving and the famine continues, they start to kill and eat their livestock.
They then eat their seed grains for the next planting (making further famine inevitable)
Next, their pets are killed and eaten.
Then the bodies of those who have died from hunger (Trupoedstvo, in Russian)
This soon morphs into murdering strangers for food (Lyodoedstvo, in Russian)
If hunger persists we see elderly relatives killed for food.
The bottom of this pit is the killing of one's own children for food. This is always furtive (obviously) but has been recorded several times. Russian famines of 1921, 1930-1933, the Moldovan famine of 1946/7 (see Burtianski, Askold Krushelnicky)
Famine, if it persists leads to a predictable pattern of "psychic decomposition" (Lee).
But not all succumb to this collapse of integrity. Even at this extreme, many simply prefer to die rather than descend so far.
Compassion can be suppressed to the point where it becomes vestigial.