Why could an accelerated education be seen as negative?

Given this knowledge of the educational system, what could be the reason that professors dislike accelerated education?

There is not a good reason, and most professors do not hold that view.

How can one highlight the advantages of having taken a fast educational route?

I have not have much success with that, and I am not sure you should try.

The advantage of accelerated education goes to you personally, not your supervisor. If you complete you degree at a younger age, then you work for more years between that degree and your retirement. As a result, you achieve more and earn more. Graduate school supervisors will not care much. It's true that students who have successfully accelerated their education are hard workers, but they are not the only hard workers.