The evidence that a horrific crime against humanity was committed by the Nazis during World War II is so overwhelming, so graphic, so vile that Holocaust denial simply labels the deniers for what they are, ignorant anti-semites of the worst kind. Those who propagate Holocaust denial win no converts. In Britain the events of the Holocaust are explained at primary school level. Jail sentences for Holocaust denial, which inherently poses no threat to anyone, serve no particular purpose other than that of political correctness, and are a threat to freedom of speech.
from the article: Spanish court rules out jail sentences for Holocaust denial