I accept it, if the sub wants a safeword. But a good sub knows that she/he shall not use it.
The moment I read it, I wanted to yell at someone. I mean, I kind of get it; the submissive should always feel safe enough in their D/s dynamic that they should probably never feel the need to use it. But to imply that a "good" submissive won't use it takes this too far.
Now, I admit I'm coming from this from my own perspective and D/s experience. That is, after all, the only perspective I am qualified to comment on. In any D/s dynamic that I have been involved in, it is true that the submissive has never had to use a safe word with me. Partially it's because I'm not "that" kind of Dominant; I'm not seeking to take someone to the absolute edge of endurance. For me, a simple "no" or "stop" suffices unless it has been agreed in advance that I should ignore such pleadings. In such a scenario, a safe word or signal is, I believe, an appropriate safety measure (the clue is in the name).
My concern with safe words is that there are some "Dominants" out there who take things too far; knowledge that there is a safe limit is seen as a challenge and they will not be satisfied until they have taken their submissve to the point where the word or signal has to be used. Now, if that is your dynamic, and you are happy with it, then that's fine. If, however, you are just testing to see how far you can go and how much you can get away with, you are treading a very fine line of which, on the other side, lies abuse.
Again, my take on D/s is that the role of the Dominat is to protect, direct, support, and nurture. That isn't to say that physical correction and the application of pain can never be appropriate because that is always up to the individuals concerned. However, being the Dominant comes with responsibilities. Inflicting pain for your own sheer enjoyment of it, and deliberately pushing the submissive beyond agreed limits is not Dominance. Ignoring the submissive's limits and actively trying to push beyond them without the consent of the submissive is not Dominance. Forcing the submissive to your will rather than earning their submission is not Dominance. There is a very short, sharp word for such behaviour and that word is abuse.
Ultimately, in my opinion, the quote above gets it the wrong way around; a "good" Dominant should never expect their submissive to use the safe word if their are truly attuned and attentive to their submissive's needs. In this context, if the submissive feels that they need to fall back on the safe word, any failing is on the part of the Dominant and not the submissive. A good submissive knows their limits and should never have to forcefully accept being taken beyond their boundaries. In their capacity as a "leader" or "teacher", a Dominant may help the submissive explore those boundaries and, if appropriate and with the submissive's consent, possibly help the submissive to widen them; but no Dominant has the right to willfully ignore those limits.
Of course, there is another perspective where the submissive "wants" to be "bad" and so will use a safe word to ellicit chastisement for their willfullness. This though, is another situation altogether. The safe word in this context isn't really a safe word at all but is a particular trigger in the dynamic to ellicit a particular response.
I guess, without knowing the actual context in which the quote was used, it is hard to have a definitive view. Applying a false context out of my own belief system is, in its own way, just as wrong. Taken at face value however, this is not a attitude I would condone; to me it borders far too much on an abusive rather than a Dominant personality.