I have no problems with blackmailers who use sexually explicit material they've hacked from other people's facebook accounts going on the sex offenders register.
If you are using material like this to publicly embarrass people; it's just another form of revenge porn. Again, stick people like that on the register.
Ultimately a person's motives can never be proven, only guessed at, but their actions have the same effect regardless.
I can't actually think of a single reason why someone might do something like this that I wouldn't then be happy placing them on the sex offenders register because of. Alleged motives count for less than the actual nature of the crime itself. Which in this case is sexual.