We have to interpret Voltaire's statements in context b/c they don't mean in context what they seem to mean out of context. He like Montaigne and others of the time pronounced on the state of things then, to the audience there to listen then. So for example, when he said, as you quote, “It is lamentable, that to be a good patriot we must become the enemy of the rest of mankind”; he mocked the notion of loyalty to the god-king that in high society was going by the name patriotism. His view was not that patriotism is an evil causing men to corral themselves in petty tribalism and war against each foreign tribe.