This is one of my favorite Luther quotations, which also suggests that those who do not battle false teachers are false and craven by default.
Retreat is often the default when something comes up - "I don't want to be kicked out." I have even had pastors look left and right to make sure nobody could hear what I was saying about their precious sect.
The first rule in our sect is - "We are perfect."
A member sent me a book about Evangelicals and was sorry it was a third-rate book. I said, no, because we need to read what is out there to know what the situation is. I read most of the Church Growth books (Trinity Seminary Library) and owned a few in Columbus. It was always a treat to watch "leaders" promote Church Growth and deny it at the same time.
We do not owe anything to false teachers except teaching them how they are wrong. Polemical speaking and writing comes from the Greek word for war. We cannot teach truth and then treat errorists with flattery, praise, and financial rewards.
When the topic came up long ago, I recalled the cartoon with the lion sharpening his claws on the whetstone. I found it and matched it with Luther's quotation. From that time on I combined a lot of great (and foolish) quotations with graphics. I can find the graphic faster than the quotation, the burden of having thousands of quotations stored.