The names have been changed to protect the innocent

[J in Florida]

With those clients that I simply dont want to work with I do one of two things, I either quote the job too high (if Im going to work for them Im going to get paid for the babysitting) or I quote it out too far and tell them I hope I can help you next time. There is never a reason, in my mind, to tell a client to go have sex with themselves.
We also have a rule in our office, the phone is always hung up before we start to yell. Its not bad yelling out but its bad to let the client hear it. Its all about emotions and keeping them in check in front of your client.
If they go on a profanity laden tirade, I simply stop talking and listen, never saying a word. Soon they will say are you still there, I will say yes I wasnt sure you were finished yet. If they go off again, I become silent again. It works .. just try it.

Great suggestions, I appreciate it. One point I will make is, once they've crossed that line, I no longer consider them as clients.