How can one claim that a well recorded event with hundreds and thousands of testimonies as well as official documents and an endless stream of research results did not in fact occur. It's like claiming there never were the Napoleonic Wars, WW1 or indeed WW2. It is clear that those who claim (not think - they know it happened) do so to promote a particular (usually insiduous) agenda. The implications of Holocaust denial are far more significant and far-reaching than the denial itself.
U.S. says working on initiative to de-escalate Syria fighting, with focus on Aleppo (Reuters)
from the article: Spanish court rules out jail sentences for Holocaust denial