Hi Marsha,

Thanks for the question.

The two vices you mentioned in your question are, in my opinion, in two different ball parks.

Smoking, for most people, is a habit that can be very hard to break.
I've never touched a "cancer stick" though both my parents were both heavy smokers.

In Christian charity, you should encourage your friends who smoke to plan for a "quit date".

Some can quite "cold turkey", like my mom did, while others may need other helps.
In both cases you should send encouraging signals to quit.

• Why?
  

Because all Christians should be pro-life and the first life they should strive to preserve is their own. By their Christian baptisms they are a temples of the Holy Spirit.

Using birth control is a more dangerous vice because a woman is not only destroying the chemistry and make-up of her own body but terminating another life.

• By not saying anything, are we partaking in their sin, especially when we know what they are doing will hurt them and others?

Yes. The Catechism tells us:

Respect for the souls of others: scandal

2284 Scandal is an attitude or behavior which leads another to do evil. The person who gives scandal becomes his neighbor's tempter.

He damages virtue and integrity; he may even draw his brother into spiritual death. Scandal is a grave offense if by deed or omission another is deliberately led into a grave offense.

2326 Scandal is a grave offense when by deed or omission it deliberately leads others to sin gravely.

You said:

• Would it be a mortal sin not to tell them what they are doing is wrong?
• Is it a mortal sin when people curse, use God's name in vain, etc.?

For a sin to be a mortal sin, it has to be:

• a serious matter
• done with full consent of the will and
• done with serious reflection.
  

If you have any questions as to whether a specific sin is a serious matter or whether your purposeful omission of mentioning something to them, is a serious matter, I would talk to your local priest or Confessor next time you go to Confession. He would be able to counsel you appropriately.

No Catholic man or woman should ever encourage any woman to take birth control without a good medical reason.

I hope this helps,

Mike

Hi Marsha,

In that case, I would just be a good Catholic witness to them and pray for them on a daily basis.
Touch base with Father too and ask for his advice!

Mike