The Report button is at the top of every post, profile, and DM message. You can open a ticket with Customer Service too, I have done that several times. And/or you can email the help line
The bigger issue is if OF actually takes action or not. They don't unless it is really clear that someone is scamming, hence all the vague DM language and emoji that Joe uses
Take the caption "Unlock if you want me to let go of the towel", he doesn't say he actually IS GOING TO let go of the towel, that way if/when people complain, he can say he never promised them anything