Strong emotions were utterly useless things, according to Spy. They caused hesitation or clumsiness at crucial moments, and Spy was perfectly happy to exploit them in others, but experience them himself? No, thank you.
He would permit himself certain emotions, of course; he was human after all, and there were feelings that he either enjoyed or was unable to surprises entirely. Schadenfreude, felt when the BLU's limped back to their base in defeat; mild annoyance, when blood splattered on his suit; a bored kind of amusement at the sight of his team's Heavy beating their Scout into a bloody pulp after some argument; a certain thrill in his blood that made his pants just a bit too tight when a wounded, half-dead BLU whimpered in pain as he twisted his knife in their belly.
These never distracted him, never controlled him, and that made them alright. But every so often, he did feel something more.
He would never say that he was friends with Sniper. To be someone's friend you had to feel more than what he allowed himself. But he would admit that they tolerated each other.
They were both colder and more detached than the rest of their team, and Spy suspected that Sniper shared his philosophy on emotion. They never really talked, but smoke-filled, companionable silence was good enough for both of them
Strong feelings simply weren't necessary.