What's The Worst Thing To Do If You're Jewish?

The Worst Thing To Do if you're Jewish is speaking against holiness. If you don't like strong mussar, or a certain strategy, fine. Nobody's making you watch. But when a person speaks against Torah with Yirat Shamayim, posts nasty comments, and destroys Kosher Torah publications like those from Rabbi Yaron Reuven, Rabbi Efraim Kachlon and Be'Ezrat HaShem, they're earning themselves a very serious punishment. While it's a mitzvah to speak against those that distort the Torah and cause people to sin, it's also a sin to speak against a Kosher Jew, and a thousand times worse if that Jew benefits the public by helping them do TeShuva.

https://www.youtube.com/watch?v=v9IQ23BgXsk