I agree completely in the abstract. It's all part of the general set of pornography. But in a relationship, webcams/sexting may cross over a boundary somewhere. If just viewing pics/vids is one side of the spectrum and actual in-person adultery is the other end, webcams/sexting is probably over near the adultery end. Maybe it will never lead to anything in the real world, but . . . It's the proximity to actual real world adultery -- maybe a precursor to it, that could be problematic depending on the situation. It's a problem that in the abstract or for single people wouldn't be an issue. It's not the thing itself, but what it's associated with.