Speculation about "an army of Lewis clones" is not (direct) speculation about Lewis becoming a tyrant, but about Lewis honestly implementing his principles. His principles say that some things we consider good are bad and need to be enforced

When there we have it. To you, and to Phil Goetz, a moral belief implies an imperative to make everyone conform to it, had one only the power to do so. The implication is so unconscious and axiomatic to you, that when you and he read Lewis saying how he thinks people should live (and he would indeed be against gay marriage, prostitution, and polygamy), you immediately imagine him imposing it on everyone, and pointing to the unwelcome result as a refutation of Lewis. Of course, the result is only unwelcome to you and Phil because you do not agree with Lewis on how people should live. But then, how will an army of Jiro clones rule, or Phil Goetz clones?

The briefest acquaintance with Lewis' writing, including the quote in question, would indicate that this is antithetical to both his written views and his life. He was an Oxford don, who once refused an honour in order not to be drawn into politics. But if you do not see a gap between "this is how people should live" and "people should be compelled to live so" then you will not only fail to make any sense of Lewis, you should on no account be allowed such power over anyone.