Going Above the Table

So I usually like to not go "Listen guys, don't do this" but I have been dropping not subtle hints the entire campaign that "this particular guy is not to be fucked with or he will make you an un-person." When they got into a pissing match with one of his lieutenants their handler was EXPLICITLY like "this is the way you guys can get at him without pissing of his boss, the BBEG." They are in a city and he is one of the most influential people in the city as well as known for just straight to disappearing people to the point that no evidence that can be pinned on him.

Today the bragadocious barbarian was set on "Just marching in there" and when some of the other players started getting on board I had to just drop the narration.

"I've been holding back. That guy that almost killed two of you? When I was planning that I thought: this is going to be rough but I think they can pull through. I've warned you over and over and over. If you do this I will not hold back, the gloves will come off and in all likelihood you will all die."

They backed down. The barbarian more disgruntled then others. Doesn't feel good but I truly could not think of another way to get through to them.

Input is welcome.