One of the surprising things I've learned about public protests in the street is that even against Hitler, they were effective.
While there were not terribly many of them, there are some that stand out - and they were open demonstrations against arrests, like those of protestant bishops Hans Meiser and Theophil Wurm in October 1934, or the protests in Berlins Rosenstraße in March 1943, mainly organized by the wives of approximately 1700 Jewish men.
In both cases, the regime caved.