Holocaust denial is a pro-genocide ideology. To deny the holocaust of the past is part of denying violence in the present day. It also implies that Jews are liars - it's a very strong piece of anti-semitism.
Can you make this case more clearly? I get that it's anti-semitic (the lying point) but not how it's pro-genocide.
Believing some Jews and other enemies of the Nazis (e.g. Allied governments) lie is not the same thing as believing Jews should be exterminated.