Capitalism has no authority to execute, imprison, or starve people into submission. Governments do.
Someone dying because another person didn't sacrifice their labor or property to keep them alive doesn't make that person a killer.
But when socialist and communist governments abolish private property, seize the means of production, suppress independent enterprise, dictate what may be produced and distributed, and punish those who resist, they deprive individuals of the freedom to provide for themselves.
There's a fundamental moral difference between refusing to provide for someone and using state power to prevent them from providing for themselves.
And an even greater difference when that coercion contributes to mass starvation.