That's a very quotable statement, and it is indeed true -- some people are intelligent and sociopathic enough that they care about their own amusement more than anything else.
But sadism is very rare, in reality. Most robbers don't give the rubies they steal to the village children. Most galloping animals with four hooves are horses, not zebras.
But the power of the internet can magnify the effect of a single sadist to the point that it affects a million people (up to the limited extent that such opportunities exist).