I don't understand why people are so willing to defend teenagers' right to do this shit. It is not smart, when the person you send the message to can forward it to everyone in their contact list. It is not a productive use of time, and in some cases it is technically illegal. No one would so vehemently defend a teenager's right to drink, smoke, or use drugs.
As for why someone would be willing to defend a teenager's right to do this shit, I can only speak for myself.
First, I would say that I liked your wording very much - the idea of defending "the right" to do it, as opposed to defending the thing itself. This is an important distinction for me. Personally, I don't care for sending naughty pictures, but I recognize that that's not a valid argument for telling other people what to do. Likewise, the opinion that something is "boring", or "not smart" or "not a productive use of time," is an equally invalid argument for banning something.
The other line of argument has to do with protecting people from themselves. An argument can be made that "sexting," is dangerous for the person doing it, but like many dangerous things - smoking, drinking, using drugs - I support personal choice, regardless. (and nothing is special about "sexting" to me - I would defend the right to drink or smoke or use drugs just as vehemently.)
As a general rule, when it comes to people doing things they might later regret - my view is that if the person consents, they're free to access whatever benefits there may be for that action, as well as free to deal with whatever blowback there is. Freedom is often a two-way street like that.
The only cracking down on this stuff I think I could support would be in specific cases, where a person sends a picture of someone else without that person's consent. I see a difference between making yourself suffer and making someone else suffer against their will.
And in cases where sending the pictures is illegal, then it's a police matter, not a school matter. If it's found that a crime has occurred, and the school wants to punish a student further (such as through suspension, expulsion, etc.), that could be reasonable. On the other hand, if the police say "We had this report of an incident, but as far as we can tell there's nothing to it," then the school should have little or no authority to act like they know better than the police. Like Celia said, schools have often punished the wrong people for alleged drinking, drug use, etc. That's because when it comes to off-campus incidents, schools (probably) wouldn't have the same ability as police to investigate an incident and determine what happened, who's culpable, etc. That's what the police are
for. So I think the school should at least wait to see what the police say before taking action, if it's something that's already illegal.
Schools
should have limited jurisdictions. They're the police of their own campus. If a student is chewing gum when they're not supposed to, a staff member can make them spit it out. Same goes for any on-campus rules. But if a school is claiming power to police beyond their borders, especially when there's evidence they won't be able to do it effectively, and may even punish students who don't deserve it because of that incompetence, then it makes sense to say no to that.
All IMHO, of course. I do have to recognize that my views on personal liberty are in the minority.