had a bad lawyer

I was cheated by a chinese lawyer in eastern coast of US.
He has advertisement in all the chinese newspaper.
I want to post an advertisement next to his, saying " I have been his client and he is
the worst layer I ever met. I deeply regret hiring him.", I will also show his name, address and
phone number in the advertisement. That information is available in his own advertisement.

The goal is that I want other chinese not being preyed by this guy any more.

I know I have right to speak my mind. I am not sure how much liabiliy I am exposed to here by
posting the above anti-him advertisemtn. I believe he probably can't sue me for that. I just want to make sure. Any idea will be greatly appreciated.