Nigel Farage sais he would 'don khaki, pick up a rifle and head for the front lines', not quite the same thing as the abbreviated version some people are quoting.
In other words, he would go to war.
He did not advocate killing. It was a euphemism for 'war', a 'war' waged against those who stymied Brexit.
On the other hand, Jo Brand was suggesting that throwing acid woukd be more effective than milkshake and there are many dunderheads who would and could buy acid quite easily, perhaps even mixing it with milkshake and think they are being funny.