There is no excuse or reason why a group should face persecution. However, the most basic reason why the Chinese regime started to persecute Falun Gong is that is what violent dictatorships do. It is what they have done to Tibet, it is what they did to the student democracy movement and also what they have done to the Uyghur’s and the Christians in China.
That being said, there are several interconnected factors and dynamics that can help shed light on how this specific persecution befell China.
Falun Gong’s Rapid Growth and Independence
Since Falun Gong’s introduction to the public in 1992 its practitioners numbered over 70 million in China in only seven years based on Chinese government statistics. As the U.S. News and World Report put it in 1999, Falun Gong had become “The largest voluntary organization in China, larger even than the Communist Party,” whose membership at the time stood at 65 million. The totalitarian Party saw Falun Gong’s independence and ability to coordinate activities a dangerous precedent, even if those activities were fundamentally apolitical and beneficial to Chinese citizens.
The Ideology Difference
All religions and spiritual practices in China must place belief in the communist party over their belief in their chosen faith, and thus many faiths that refuse continue to be persecuted today.
In spite of China’s turning to a market-economy in recent decades, the atheist Communist Party still clings to an officially Marxist ideology (even if few officials actually believe in it). Some Party leaders saw Falun Gong, with its belief in the existence of Buddhas, Daos, and gods, and its conviction that anyone can reach a divine realm through self-refinement, as being in conflict with Party ideology.
Others feared that Falun Gong's moral code undermined the Party's Leninist tactics for controlling society. Where Party-controlled media deceive the public, Falun Gong emphasizes truthfulness; where the Party calls for people to struggle against each other, Falun Gong urges kindness; and where the Party uses violence to enforce its will, Falun Gong teaches strict nonviolence.
Jiang Zemin’s Jealousy and Opportunistic Maneuvers Played a Decisive Role
Jiang Zemin was the leader of the CCP at the time. With a handful of supporters, led by Luo Gan, Jiang dictated the anti-Falun Gong stance by presenting the group as the biggest threat to the Party, labeling Falun Gong an “evil religion ”, creating the 6-10 Office, and pushing forward legislation to retroactively justify the ban.
There are two reasons why he did such a thing. First, journalistic accounts and inside sources suggest that Jiang was acutely jealous of Falun Gong’s popularity and saw it as undercutting his own legacy.
Second, as CNN analyst Willy Lam and others have suggested, Jiang saw an opportunity—by attacking Falun Gong and creating a Maoist-style campaign, Jiang could use the campaign “to promote allegiance to himself” and maneuver to gain politically (see CNN report).
Why has the campaign continued so aggressively even after Jiang's retirement? Jiang arranged for members of his political faction to remain in top positions within the Politburo and Party security apparatuses. These people have been able to maintain and even intensify the campaign. Reports from inside China, however, do reveal increasing tensions between Jiang’s faction and the new leadership.
Also, these officials may now fear responsibility for crimes against humanity thus it would be in their best interest to cover up these crimes by continuing the persecution.
Chinese Regime Propaganda against Falun Gong
The number one weapon in every genocide in history is propaganda which is used to stop public support by painting the victim of somehow deserving of what is happening to them.
Chinese officials main stand is that Falun Gong is banned because it is a menace to society, an “evil cult” and any rational government would do the same.
The problem with that theory is the Communist Party is the only government to have banned Falun Gong while it is practiced freely around the world in over 70 countries since 1994 without incident. Also, just 100 miles away in Taiwan Falun Gong is practiced freely by hundreds of thousands of Asians. It is embraced by officials who praise it, students take it for extra credit, and it is taught in jails to prisoners as part of their rehabilitation program (report).
Similarly, a wide range of international bodies—including United Nations Special Rapporteurs, prominent human rights groups, and democratic governments—have repeatedly referred to the campaign against Falun Gong as one of unjustified religious persecution rather than as a legitimate government policy to rid society of a supposedly negative influence.
Jiang Zemin used application of the "cult" label three months after the persecution began to shift the spotlight from perpetrator to victims, undercutting sympathy for Falun Gong, and retroactively justifying the ongoing arrests of tens of thousands of innocent people. The regime then created damning incidents that they attributed to Falun Gong, like the infamous “self immolation” (report) to fuel their campaign of public hatred towards Falun Gong.
In fact, as noted by Human Rights Watch in their 2002 report that analyzes why and how the Chinese government embarked on a plan to eradicate the group it terms an "evil cult," they state:
“Falun Gong members are peaceful, law-abiding citizens, and there is no excuse for the human rights violations they have endured. The charge that Falun Gong threatens the stability of China does not hold up. Its claim that belief in Falun Gong is a public health menace is equally bogus. The danger to health comes from the treatment its practitioners receive at the hands of the police and prison officials."