"For instance, a bad fellow like Wang Ming plays a good role as a teacher by negative example."

http://www.prisoncensorship.info/archive/etext/classics/mao/sw5/mswv5_57.html



Wang Ming, who had previously made the mistake of 
pushing a "Left" opportunist line, now made the 
mistake of pushing a Right opportunist line. He 
had first carried out the ultra-Left policy of the 
Communist International, and this time he carried 
out an ultra-Right policy. He too was one of our 
good teachers by negative example and he educated 
our Party. We had another good teacher by negative 
example in Li Li-san. Their chief mistake at the 
time was dogmatism, transplanting foreign 
experience mechanically. Our Party liquidated 
their erroneous lines and really found the way to 
integrate the universal truth of Marxism-Leninism 
with the concrete conditions of China. As a 
result, in the fourth period when Chiang Kai-shek 
launched an offensive against us, it was possible 
for us to overthrow him and found the People's 
Republic of China.

The experience of the Chinese revolution, that is, 
building rural base areas, encircling the cities 
from the countryside and finally seizing the 
cities, may not be wholly applicable to many of 
your countries, though it can serve for your 
reference. I beg to advise you not to transplant 
Chinese experience mechanically. The experience of 
any foreign country can serve only for reference 
and must not be regarded as dogma. The universal 
truth of Marxism-Leninism and the concrete 
conditions of your own countries--the two must be 
integrated. 

Mao talking to representatives of Latin American communist parties

http://www.prisoncensorship.info/archive/etext/classics/mao/sw5/mswv5_54.html

The Wang Ming Line had the longest life-span. He 
had formed a faction in Moscow, and organized the 
'28 1/2 Bolsheviks'. Relying on the might of the 
Third International they seized power in the Party 
and held it for a full four years.

http://www.prisoncensorship.info/archive/etext/classics/mao/sw9/mswv9_88.html

Two of the leftist trends were our own, and the 
third leftist trend and the Communist 
International were related to each other. The 
Fourth Plenary Session's resolutions on the third 
leftist trend were written by the Russians who 
forced us to accept them, especially the Wang Ming 
line. It was the greatest loss to our 
revolutionary power, the loss incurred amounting 
to over 90 percent. In view of this lesson, we 
should accept things analytically and critically.

http://www.prisoncensorship.info/archive/etext/classics/mao/sw7/mswv7_468.html