St. Thomas gives guidelines about when correction is required or even permitted, and evangelizing is in that category.
You have an obligation if you're someone's superior and therefore responsible fro them to a point.
You also have an obligation, to a point, with those you have duties toward, such as a spouse or your parents, because honoring them involves doing all you can toward their salvation.
But the biggest is the prudential consideration. Will whatever say do ANY good whatsoever? In some cases, it might make it worse and make them push even farther away. So it's a judgment call.
Basically, pray for the person, and ask the Holy Spirit for hints about where He might be inviting you to intervene somehow.
Yes, Ladislaus saved me some typing as usual.
Don't cast your pearls before swine. This is a common mistake of the Protestants.
HOWEVER, if you're interested in fulfilling your duty before God, then LEARN YOUR FAITH WELL
. We live in a post-Christian society. We are surrounded by infidels and heretics. Become an apologetics expert. When non-Catholics ask questions about the Faith, the Mass, the saints, statues, sacraments, sacramentals, Church history, praying to saints, the Blessed Virgin Mary, the Incarnation, the exact nature of Jesus, etc. you should have answers to ALL THEIR QUESTIONS.
I'll tell you this: when someone asks you an honest question, or when someone is seeking the truth and investigating the Faith, and you (a known Traditional Catholic) is forced to shrug and mumble incoherently "ahuhnoh"
("I don't know"), you will probably have to answer for that later at your Judgment. Can you honestly say that God didn't give you the brain to remember/understand, and didn't give you enough time to read a couple books? I would never be so bold to accuse God of either of these things -- but there are some who are retarded, etc. and they are indeed off the hook
. If you're really going to claim "too busy" you better be right -- you better not be wasting time, because you can't fool God, even if you can fool yourself
You never know when you will come across an honest seeker of truth, a person of good will. That person's salvation might depend on YOU picking up that Catholic book in your hour of downtime, instead of turning on the TV, firing up the gaming console, or kicking back to waste another hour on Youtube.
I wish I had a nickel for every time I found reason to bring up something I just read in a Catholic book (whether the book is about a saint, apologetics, history, doctrine, spirituality, etc.) in the next week after reading it. It's an amazing coincidence that seems to happen to me a LOT. If I really got a nickel for every time my studying the Faith has come in useful, I'd have a lot more square feet around here: I'd be able to put up another house on my land.