Well, it’s certainly tradition and in the RCC mind it may be sacred, but it is not by any means true because it’s contradicted by the clear teaching of Scripture.
So the appeal to *Sacred Tradition* may make people feel all warm and fuzzy, but is nothing of substance.
And it’s “Sacred Tradition” per the RCC who after all is infallible when making decision of “faith and morals”. It had to be moral to kill all those “heretics” in such horrendous ways. That was moral per the RCC evidently.