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“Love, John! Surely you don’t think it out of the realm of possibility for a man to sacrifice himself for one he loves?” Sherlock said.
“Hang on - love?” John stammered. “How many times - I’m not gay!”
“Don’t be an infant, John. Don’t confuse love with lust.” Sherlock turned to make sure he had his friends complete attention. “Lust makes a genetic legacy, John. Love... love is what makes families.”
John opened his mouth then shut it. Sherlock rolled his eyes in exasperation.
“Honestly, John, you’ve studied comparative biology. Human young are entirely dependent for years after birth. Lust may make children,” his mouth twitched when he said it. “But it doesn’t make fathers, and it certainly doesn’t make husbands.”
John blinked, the curious mix of surprise and incredulity that so often accompanied his conversations with Sherlock shown plainly on his face.
“Oh come on, you are a military man, are you not?” Sherlock brought his hands together beneath his chin and paced the short distance in front of the hearth. “What entices men to fight in a war? Thirst for violence? Possibly, more likely patriotism. And what is that if not love of one’s country? ‘Home and hearth’ as it were, but perhaps that’s just loyalty.”
His stride extended in agitation as did his gestures. “What holds a unit together when they’re cut off from their central command? Discipline? Maybe...But a small group abandoned behind enemy lines? Pure survival instinct?” Sherlock slapped the table, setting cups and plates rattling. “Then what makes a sniper carry his spotter’s body through hostile territory at risk of exposure and death... just so he can be given a proper burial?” He was breathing hard now and a fine sheen of sweat coated his brow. “Love, John. It’s why people do most things, hard things anyway.”