Jo Brand, whether you find her funny or not, earns her money as a comedian. This was said as a follow up to Farage being hit by a milkshake with the idea that battery acid rather than milk was what he deserved. It obviously wasn’t a serious suggestion.
It was though a poor joke, held to be inappropriate by the BBC and in bad taste.
By the way the audience on Twitter was far from a handful. It was several hundred thousand, many of whom would have been following her because they hold similar political views. They were likely to take the words seriously and react. Not treat them as a joke in bad taste.