"it removes other people's loneliness"

Even the idea that people get lonely is a clue as to how much people need other people. People have evolved to need each other, to feel positive feelings when they cooperate with each other. To love each other. Empathy is a subset of that overall human operating software.

Your sociopath, by contrast, is not normal, precisely because the parts of the brain that make empathy happen don't work.

Empathy is Darwinian, weirdly. Tribes with empathic members thrive, because those who fall behind get lifted up. If you have a soldier willing to give his own life for others, your side is more likely to win a battle, and be a surviving tribe. Imagine if a disaster looms, and noone is willing to give their life to save everyone else: then everybody dies.

Without empathy in a tribe, a war of all against all wears everybody down. Everybody ends up losing out. The tribe without empathy dies out ultimately, where the tribe with empathic members thrive.

It's only empathy (and sympathy) that prevent perpetual competition and war, amongst individuals, destroying the human race. Humans are so successful as a species precisely because we are programmed to need each other, and serve each other, and our brains affirm such actions with positive feelings. We are a social species. :)