How the two are alike can be stated clearly. AT: "A proverb in the mouth of fools is as dangerous as a thorn that goes into the hand of a drunkard" (See: [[rc://en/ta/man/translate/figs-simile]])
Possible meanings are 1) if a drunk person holds a thornbush, a thorn will prick his hand, or 2) if a drunk person is angry, he will pick up a thornbush and swing it at people. For the second meaning, the word "thorn" represents a thornbush. (See: [[rc://en/ta/man/translate/figs-synecdoche]])