If you don't have enough time to rebut the entire article, you can at least disapprove one of your opponent's opinions with reason and facts.
Denouncing your opponent with empty words full of emotional hatred, such as "crazy", "stupid" or "disabled mind" doesn't help anything.
If you do want to write something powerful that will convince the general public of your argument, please address the following with facts:
Deng's ruling elite has indeed improved China for the benefit of the majority Chinese population during the later 30 years, in terms of
1. GDP, 2. Environment protection, 3. Polarization between the rich and the poor, 4. The fairness, transparency and cleanness of the government, 5. the morality of the Chinese society, 6. the 8964's killing for the protection of the corruption didn't happen, 7. the rampant corruption since 8964 is false.
If your rebuttal doesn't address the fundamental issues as listed above, then you have no chance of wining the public opinion if a democratic China is truly your goal.
The fundamental rule behind the freedom of speech is that even an evil is allowed to have his free speech. If one doesn't know this fundamental, then his freedom-of-speech is only empty word.
The ruling elite in power always labels its opponent as an evil, then deprives the freedom of speech from the opposition.
There were countless tragic incidents in the human history, that brilliant scientists were labeled as evils, the open-minded intellectuals were persecuted due to their opinions different from the ruling elite.
China's rightwing extremists, in the name of democracy and freedom-of-speech, are fighting hard to shutdown the voices of the common people, and they only want the freedom of speech for the rich and themselves, and don't tolerate any opposition. This will push the majority of the Chinese population to the left, eventually push China's left-wing extremist into power. Just as the right-wing extremist doesn't give a dime to the freedom-of-speech, the leftwing extremists will not tolerate any voices of the right-wing extremists in the name of majority rule.
Now, China's rightwing extremists are on the upper hands, who can do whatever they want. I hope that these rightwing extremists would not complain about their having no-freedom-of-speech when they are treated in the same way they treat the leftwing extremists, when the leftwing extremists are in power.
The best way of attack is to criticize the article paragraph-by-paragraph, that is, giving rebuttal to the article from one paragraph to another with reason but not with emotion. Calling an author "crazy" doesn't carry much weight in defeating the opinions of an author. The public judges the right and the wrong on an article mainly according to the fact that whether the article is helping in promoting the fairness and cleanness of the Chinese society, and whether the article is revealing the historic truth about the great improvement of the living standards of the Russian people since the downfall of the Soviet Union, about the rapid decrease in China's polarization between the rich and poor, about the dramatic decrease of the government corruption, and about the alarming decrease of the rich Chinese people flying abroad.
Freedom of speech shouldn't be interpreted as allowing the freedom of speech only for one school of thought and only for the rich. One needs to allow the freedom of speech for the poor, for the majority of common people, and for the people who have not been controlled by money yet. It is amazing that so many so-called supporters of the freedom of speech are suddenly calling a different school of thought as "crazy". The nowadays Chinese media is mostly controlled by the money and the powerful, which is of the money, by the money and for the money.