I like Jo Brand and think she is usually very funny and insightful.
When judging this remark, I wondered how I would feel if somebody whose I dislike intensely and whose political views I vehemently oppose made the acid throwing remark. My conclusion was that I wouldn't like it as, although it was obviously a joke, it trivialises acts of violence.
It was a joke but, in my opinion, a very ill thought through joke.
Having said that, I still like Jo Brand and hope she is not sacked.
It has given a wonderful opportunity to those constantly blame "lefties" for all the evils of the world - they are, of course the only people to make tasteless jokes or incite and commit acts of violence.