No. of Recommendations: 2
...but they're not going to just because we want them to, or even because we threaten them.
Exactly. You don't threaten, you don't draw lines, you don't trail the Navy's coat along the Red Sea with a big SHOOT ME sign dangling from the fantail. You...do. As in, you find something they value and you eliminate it. Quietly and without much fanfare until it's done.
The Behshad lacks the capability to defend itself from an attack - literally every country in the region has the physical ability to sink it, if they wanted to. The reason that none of them have - even Israel - is because sinking the ship isn't worth the consequences that would flow from sinking it. It's no small thing to destroy a ship lawfully present in international waters, using your military to kill the citizens of another sovereign nation.
There are numbers of ways to send a message. A low level flyby at Mach 1.1 from a couple of F-15's would send a nice message.