There's some truth to this that's worth pausing on.
But it's a fallacy (probably with a fancy name) to say "it made you mad therefore you worry it's true".
A statement could be false yet incite anger because it's demonstrably harmful.
This makes it a useful measure sometimes. If a thing you say causes anger, it may or may not be true—but it definitely indicates your counterpart’s sensitivity to and bias against it being true; the chance of it being false is thus elevated.
Making it more personal: Would you get angry were someone to falsely accuse you of a crime? Would it frighten you? Would those emotions come from a lack of confidence in the truth, or a lack of confidence in your support system and, ultimately, the justice system to separate fact from fiction?
Fear is natural if hate has the potential to spill into action, but anger is a signature behavior of a cornered creature—it will not lend credence to any of your counter statements and is useful in a very, very limited range of scenarios. Keep your cool.
To circle back to the topic at hand, any anger stems from fear/insecurity (which may or may not be warranted); when it happens unexpectedly when discussing a random topic, like in TFA—no one wishes death to anyone, and yet someone gets mad—then it is a useful indicator.
The thing is, if you really want to prevent antisemitic violence, censorship is not going to help. If someone claims that the Jews rule the world, you can argue, “so why did the Jews end up on the wrong side of the Shoah” and if they claim the Shoah didn’t happen, you bring out all the documentary evidence that it did happen. If censorship is on the table, the anti-Semite can—as he does in many countries already—censor all of the documentary evidence that demonstrates the barbarity of his position.
Is he trying to say that there's nothing moral under the sun? That there are no evil ideas? Do I even need to put forward examples?!
And providing no framework or tools to distinguish between the two and just telling everyone "go for it" is dangerous. I'm mad at the idea. And no. I don't think it's because it might be true.
"You should tell the truth" yes, probably you should but should you always? what if you can prevent trouble if you lie? what if you can save someone form getting hurts by lying? what if you omit something etc. etc.
"You should not take a life" except if self-defense, defense of someone else, if the person poses an imminent danger to you or someone else, the person is military personnel form a different country, the person is unborn etc. etc.
But failure to articulate universal moral rules concisely, doesn't mean there's no concensus.
Circumstances and relevant context can be very complicated and laborious to describe, but there are still many cases where overwhelming majority of people would agree on what's right and what's wrong.