Yes, because they remind us of our past. If we take them down, its as if were trying to forget or erase our history. If we are not educated on history, then we are doomed to repeat It. Germany rebuilt some of its concentration camps as a reminder for their history and that it was a bad thing.
Prison Labor is legal but not so commonly used anymore. There are still other forms such as community service.
Different ideas, cultures, religions, lots of factors.
Somewhat hostile, as they took the Iberian pynisua from the ottoman with the help of the crusades. The Spanish then killed all Muslims who would not convert to Christianity under King Ferdinand