Safety of Flight is the easiest card you have in your hand as long as you are being honest, and do not cave no matter how much pressure is brought. I've called it a couple of times in AMC and while TACC went apeshit, my local OG had my back. TACC wants to make it more of an asspain for you to "stop" a mission than it is to "go", so don't play their game. When you call them and declare safety of flight they will want you to "call back to your OG before declaring". Don't bite. Tell them you are arranging Billeting for your crew, and will give a contact number once in Billeting. They will want all the details immediately. Details can wait, you need to get you crew to bed. If they continue to badger, get them to explain, on a recorded line, what they are asking you to do i.e. "So what you are saying is you want me to fly exhausted after I just told you how unsafe I believe it would be?" That usually gets them backpedalling and they capitulate. Another tactic is they will ask "Who is your Ops Group Commander? Because he will have to be notified." I've never bit at this, but if it happened again, and I was sufficiently pissed, I would ask who HIS supervisor was because HE was going to be notified of a crew being harassed over safety.
I've never heard of a pilot being disciplined for calling safety of flight, but there seems to be some fear of doing it (perhaps the TACC inquisition routine). As long as it is legit, call it, and never back down. In an ideal world TACC should say "Thank you for making the safe decision, let's work on getting your crew some rest".