There’s no doubt that New York City Mayor Michael Bloomberg is a foe — not a friend — of liberty. Still, Jonathan Tobin reminds Commentary magazine’s online readers that comparisons of Bloomberg to Adolf Hitler ought to be completely out of bounds in our political discourse.

Glenn Beck’s appearance at last weekend’s National Rifle Association convention is the sort of thing that cannot go without comment here. In his remarks to the conclave, Beck denounced New York Mayor Michael Bloomberg for financing campaigns against politicians who defend Second Amendment rights. Placing it in the context of Bloomberg’s nanny state style of governing New York, which has led to soda bans as well as a myriad of other measures designed to tell people how to live, Beck put forward a critique of the mayor that rightly painted him as an opponent of individual liberty. But then, as he has often done in the past, Beck went too far.

It wasn’t enough for Beck to depict Bloomberg as a nanny state petty dictator. Instead, he spoke in front of a large backdrop that photo-shopped Bloomberg’s face into a famous photo of Adolf Hitler with his arm extended in the infamous Nazi salute. This is more than merely unacceptable political commentary. It is an offense that diminishes the horror of the Holocaust and casts a dark light on both Beck and those who thought his little joke was funny.

In writing this, I can already hear the complaints of conservatives who will say those of us who oppose Bloomberg’s politics should not attack Beck since that undermines the cause of defending gun rights as well as the cause of liberty that Beck said in his remarks was his sole motivation. But anyone who doesn’t understand the difference between an anti-Semitic mass murderer and a liberal American Jew need not bother deluging my email inbox with their pointless criticisms. Calling liberals Nazis doesn’t hurt liberalism. It hurts conservatives. Making such comparisons is not just a manifestation of a lack of good taste or an unwillingness to treat the Holocaust as a singular historic event. Resorting to attempts to delegitimize the other side is a sign of an inability to make reasoned arguments.