Although it would be unethical for the Snapchat folks to do a statistical sample to find out, I'd estimate that sexting is no more than 1% of Snapchat, probably more like 0.1% or 0.01%.
This seems like the type of video I'd expect in a response on Reddit. That is, it's a response that's trying to be funny (or link something funny) rather than continue the conversation at hand.
I was really hoping it would be a link providing evidence to one side (Snapchat is primarily sexting) or the other side (only a small % of snapchat usage is sexting).