Milord On a minor, because it misses on point 4,
I basically agree with your argument, but on this one aspect I have some doubt.
1) Obviously, it is worthy of the highest condemnation if parents force a minor to wear a chastity belt using a relationship of dependence. But don't you think that a person of, say, 16-17 years of age (and therefore mature enough to have sex legally in almost all European countries) is mature enough to be able to decide that his or her body is restricted to some extent? A good such as freedom can, after all, be restricted quite freely with the consent of its possessor. I ask because I have had a similar experience myself - I got the belt when I was 17, but my parents did not in any way force me to wear it, I did so entirely voluntarily.
2) In your opinion, can a minor who has reached the age of consent legally participate in BDSM practices? In my opinion yes, although I know this is rather frowned upon in the bdsm community.