Because the man appears to be contradicting himself. “If I tell you something that contradicts your beliefs don’t listen to me’’. What exactly does that mean?
Except that’s not what he said. He said if I tell you something that contradicts the catechism don’t listen to it. And it means exactly what it says. It’s essentially what Paul told his readers in Chapter 1 of Galatians.
I get what you’re saying. There are some potential problems on a philosophical level. If a priest says, “Ignore priests/bishops/cardinals/popes if they’re teaching something contrary to the Catholic faith,” but you believe that the Catholic faith requires you to NOT ignore priests/bishops/cardinals/popes, then you might be in some kind of endless loop of logic in deciding whether to follow this particular priest’s advice. Fair enough. But life isn’t a philosophy class. And if you start from the premise that it is possible for any one particular priest/bishop/cardinal/pope to teach error, which seems to be obviously true as of 2020, then the advice to ignore priests/bishops/cardinals/popes when you believe that they’re teaching error seems like sound advice in my book.