That communism doesn't work is blatantly obvious. Referring to communists ... I guess there are lazy as well as hard working people in any believe system and / or religion (which communism basically is). However - a system which rewards lazy people over hard working people by paying everybody the same rewards obviously attracts more of the lazy category - simple rule of the market.
Similar situation as with the Catholic church - a job which (at least used to) give easy and trusted access to vulnerable children used to attract an unproportional high number of pedophiles.