Sexting, though not because I see it as a threat. Apart from child porn, assuming a definition of that can be found that is satisfactory, I'm not sure what about either porn or sexting is threatening.
If there's harassment, it's not the medium, it's the message-giving. Or to put it another way, its not how you sext, but when and to whom. Same with porn -- if you use it to hassle someone ("boy, you'd look great doing that"), it's harassing. If you use it to fantasize about someone in your office, its just..well, porn.
IMO the worst part of sexting is that is like bad porn. Frankly, I can't imagine anyone ever sexting me a picture of certain body parts, but it they did, frankly, it would tell me the person is a complete loser. "Yeah, it looks something like a penis, only smaller" comes to mind as an appropriate response.
It's like walking into a bar, walking up to the first attractive stranger you see and say, "Hey, babe, wanna fuck?" It's just bloody illiterate. If sex isn't anything but putting a outie into an innie for you, well, all I can say is "yech."
Everyone knows that porn is the number one Internet industry, by far. But does anyone ever ask why it's such a big industry? Apart from the temperance freaks, femonazis, and other assorted repressed moralizing who think it means all men are sicko rapists and white slavers at heart?
You don't make money at something, and you certainly aren't going to make gazillions as porn does, unless you are providing a crapload of value to someone (i.e., the buyers). Take all the pedophiles and the rapists and the wife abusers out, and I'm betting that instead of 10 gazillion dollars of revenue from porn, you're going to find 9.9 gazillion dollars.
The fact is that porn has an incredible diversity to it. It makes gazillions because it sells hundreds of different kinks, perhaps even thousands. And the "threatening" kinks are a tiny fraction of the whole.
Sexting? I doubt if it could handle even two or three variations. Distinguishing between the kinds of porn demands a weird sort of intellectual sophistication. Sexting ...it's just an electronic version of the caveman's "Ug. Me hump. Ug."
Of course, that sophistication does hide one danger that the caveman never had to worry about: addiction. I have a hard time imagining a sexting addict -- you can't become an addict if you have no brain cells for the addiction to play on. But there are all kinds of porn addictions out there for the temptation.
For many, porn is the ultimate "designer drug". You get to pick your own side-effects. And so if you've got a capacity for addition in you, porn can help you exercise that capacity.
On the other hand...if you're addicted to something that makes you happy, is that truly "bad"? Oh, I might think you're weird or disgusting or be completely mind-boggled that you get into women coated in chocolate or cross-dressing or whatever. Heck, I might even think you're engaging in idolatry that is going to damn you for eternity.
But unless you try to share that kink with me, frankly, it's none of my damn business. And it doesn't bother me -- damnation is God's job, not mine.
The only thing that would bother me is someone bothering me after I've said not interested.
Or someone think I need protection from someone into porn or sexting, just because they might be into porn or sexting.
Most porn users -- and, I expect most sexters -- know what the meaning of "no" is. Just like most co-workers will, when the sexy co-worker says no to a request for dinner, take no for an answer.
People who don't take no for an answer. People who don't ask. They are the slugs. The threats.
And do not be conformed to this world, but be transformed by the renewing of your mind, that you may prove what is that good and acceptable and perfect will of God.
Romans 12:2 (NKJV)