To paraphrase the old wester adage, "You don't have to be crazy to protest in China, but it help".
And if you don't happen to be crazy, there is apparently nothing to
stop the state from saying that you are, and locking you up.

According a reports released by the New York based human rights group 中國人權 (Human Rights in China) , Liu Xinjuan, a prominent 上海 (Shanghai)
land activist who is well known for her efforts in fighting forced
evictions and illegal land-seizures, was detained earlier this week,
and committed to a mental institution on state orders.

Although
there has been little official word on the reasons for Liu's detention
and subsequent committal, sources indicate that she was seized by
Chinese security force in 静安 (Jiang'an) District Park, Shanghai, on 16 January.

After her seizure, Liu was taken to a secured compound, thought to be the Qibao Dispatch Station, in 上海 (Sanghai)'s 闵行区 (Minhang
District), where she was interrogated by security forces for several
hours, before being transfered to the Beiqiao Mental Hospital. Where
she was committed for 'treatment' on the grounds that she was 'mentally
unsound'.

Reports indicate that Liu was 'bound and gagged' during the transfer, and that she had been badly beaten while in custody.

Prior to her detention, Lui had been attempting to meet with fellow activists in 静安 (Jiang'an) District Park, in preparation for a march to deliver a petition to state official meeting in the Sanghai Sino-Soviet Friendship Building.

"litigation mania"

Although
not often spoken of, it is a well known for Chinese authorities to
commit persistent protectors and activists, like Liu, to mental
institutions, under the claim that they are suffering from persecution
complexes that cause them to mount 'irrational campaigns of harassment'
against state or corporate interests.

This condition has been
colloquially dubbed "litigation mania" by Chinese Police psychiatrists,
and authorities claim that, by detaining activists in mental
institutes, they are 'serving the public good' and 'protecting
stability.

However, "litigation mania" and the detention of
activists in mental institutions has been categorically dismissed, by
human rights interests, as being 'an excuse' to detain persistent
protectors outside of the normal judicial system, and as a tool to
discredit them as being 'mentally unsound' in a country where mental
illness is still not publicly understood

Liu was previously committed to a mental institution in 2003 because of her protest activities.