Here are some good examples, which I will mostly paraphrase:
Q: My young kids accidentally smooshed their hamster, and I bought them a new one to protect them. Is it okay that I lied?
A: Your kids are not as stupid as you think they are. They know they killed the hamster. Now that you brought a new and live hamster home, they are doubly confused and think their hamster has "Wolverine-like" healing abilities. Tell them the truth and stop being stupid.
Q: I am infatuated with my wife's hot sister. I love my wife who just had our first child, but she is just not as sexy as her sister. I told my wife. "Now she feels I don't want her. She also doesn't think her sister would ever 'want' me (not sure how to take that one)." What should I do?
A: Don't tell your wife that you'd like to "bang her sister." Also, you need to forget about her sister and focus on your wife who just gave birth to your friggin' child and probably feels asexual right now. "You also seem to be insinuating that you're insulted that your wife thinks her sister is not interested in you. Which prompts some more advice: Grow up. You're an adult and a father, so stop acting like a horny teenager."
Q: My mother tells me that she sees my sister and her kids every day and does everything for them. However, I live far away and hardly see my mother. I feel jealous of my mother's involvement in my sister's life. Boohoo. Can I tell her to shut up about it?
A: Let's imagine the letter your sister might write to me: Please save me from my mother who won't leave me alone. She is great with my kids but drives me crazy. I wish I was my sister who is far away and can do whatever she pleases. So stop crying!
Awesome, right? People who write to Dear Prudence are going to get brutal honesty. Love it!