There are a few reasons why I believe it's important to separate intelligence from moral goodness
The first and most basic is because they are different things, and for the sake of clarity different things should have different words to refer to them.
The second is because it allows us to have intelligent conversations about people who are intelligent but morally bad, or who are unintelligent but morally good. The person with an IQ barely above that of the strict definition of mentally retarded (or below, but questions of agency and responsibly arise so we won't use them in our example) who recognizes the humanity in every person and volunteers at the soup kitchen every chance he gets is morally good for doing so. The 180IQ engineer who manages the highly complex train schedule to keep the extermination camps running at capacity is morally bad for doing so.
The third is because it allows individuals to recognize that blind respect of intelligence which is unguided by morals or wisdom is a fool's errand.
The fourth is because is prevents the moralizing of language from hampering the clarity of language
The fifth is because the conflation of intelligence and morality provides an easy pathway to morally wrong positions. If the messaging is that "evil people are dumb!" and an impressionable individual encounters an intelligent person making a persuasive argument for something which is morally wrong, you've robbed them of a framework with which to engage and combat this person's ideas.
The sixth and final reason is that modification of language in this way hampers our ability to consider the world independent of our societal preconceived notions. I found the previous comments in this chain ironic because the individual who was calling a great (highly intelligent) philosopher a dunce for being unable to see beyond his cultural ethical norms was doing so from a position which is deeply entrenched in his current cultural and ethical norms, i.e. the inherent evils of slavery, the requirement of strict moral purity, the compulsion to attack every perceived positive characteristic of someone who is morally bad in order to devalue them and their intellectual contributions, and the perception of the world as a pitched battle between good and evil wherein righteous indignation should be one's perpetual state.
Now of course I agree with this commentator's ethical preconceptions related to slavery, but that's secondary to the importance of the things I listed above in how I approach Aristotle. I mean no disrespect and I hope this has been helpful in understanding my perspective.