By Leibniz's logic in the Theodicy, you cannot know that your final statement is true: that it is possible to have the best possible world without evil. If God is omnipotent, in fact, you have to assume otherwise. For instance, if heroism, is truly valued, it would be difficult to display it in a world that lacked all aspects of evil.
Negation being a human concept, the idea that the absence of evil is good does not necessarily follow logically from anywhere. The theological position known as 'privatio boni' suggests that evil does not exist as a real thing, and that we create it out of our understanding of 'good' and of 'lack'. But even lack is good: we can only really be fond of what is occasionally lacking, or we would never notice it. So we are creating 'evil' out of two good things, making an obvious error, though perhaps a necessary, human one. By that argument, were there no evil, we would still perceive it, and thus create it. It is not a product of God's (or Satan's), but of ours.
In a popular Catholic interpretation, an amplification of Augustine's "Dubito ergo sum", the best possible world may teem with evil, especially self-doubt, so that there are ubiquitous opportunities to address it and become stronger.
From those points of view, there is no argument here, because one of the two contending premises is a complete misunderstanding.