Unwarranted stricture

The biblical regime deals with the challenges of avodah zarah while the rabbinic regime does not. 

When the Jewish people were confronted with the aggressive threat of the Nazi ‘evil as policy’ the Jewish leadership failed to recognize avodah zarah when they saw it. Instead, they read the familiar into the strange and judged the Nazi threat to be merely a variant of the old despotisms – something the people could weather successfully. 

Here is why it is dangerous to add stricture (chumrah) where it is not warranted. Because too many benign practices had, over the centuries, been designated as avodah zarah, by the time the Jewish leadership came up against real avodah zarah face-to-face they didn't understand what they were seeing, and they were lulled into a false sense of security.