Sarcastic people are brutally honest. They don’t beat around the bush and they don’t sugarcoat ugly and harsh truths so as to make them appear more positive or pleasant than they really are.
They’re not afraid to give you a verbal slap in the face if you’re acting a fool and really deserve it. You should expect to hear the truth, the whole truth, and nothing but the truth. Trust me, it’ll be better for you in the long run. And if they notice that someone is trying to manipulate you or lie to you, they won’t think twice about revealing that person’s intentions and protecting you from them.