Pray to the Holy Ghost. There is no one proper thing to do. It very much depends upon the identity of the blasphemer and your relationship to him/her. If it’s your child, it’s time for a many smacks with the board of education on the seat of learning. Talk, pray, impose a penance, a chore the child hates, or revoke privileges. Take the child if old enough, to Confession.
If the blasphemer is your boss, I’d refrain from striking him/her. You might write him a handwritten letter, (no internet!), register a complaint with his superior or HR. Or go to him with another worker whose judgment he respects. Pray. If it’s a chronic problem, you might quit. Give proper notice unless the blasphemy is aimed directly at you, or is particularly outrageous, turn around, say nothing, pack your office, and leave a note.
If the person is a total stranger, say, in a public place, certainly do not get physical. You may politely rebuke the person in a calm tone of voice, but you are not obliged to. In some instances, silent prayer may be the best reaction, and try to remove yourself as soon as possible from the blasphemer. Whatever action you take, you must be willing to take the possible consequences without complaint.
Example, you haul off and backhand a bulked up gang member in the subway, be prepared to physically fight the person, be stabbed, or even shot.
Usually, a middle ground is called for.
Here’s an example from my life. I was visiting the home of a relative about my age, 30ish, who still lived with her parents because of mental health issues. The person was not intellectually impaired. I volunteered to help her clean her car. In the process, she kept blaspheming Christ out of very bad habit, but it WAS within her control because there were certain people around whom she never swore. I gave her several verbal warnings, then a stronger rebuke. She kept on blaspheming to see how far she could go. I took her aside and said, “Ann, (not real name), if wish my assistance, you must stop swearing. If I hear it again, I won’t give you another reminder, I will stop and go home.” She glared at me, thrust the wand of the shop vac at me and said, “Quit giving me a sermon. Get busy vacuuming the |]§£¥>, #$&*, floor mats. $&@!”
I put the wand down, turned and calmly walked back to the house. She continued yelling, followed me inside, threatened to blank herself and go to Hell. It would be MY fault!
I didn’t respond, although her parents got all upset, also yelled at me things like, “She can’t help it. Last time she cut herself and we had to put her in _____hospital…”
I responded to her parents, “Yes, she CAN help herself.”
I got my bag, thanked them for the nice lunch, got in my car and drove away.
Naturally, she did not eliminate herself, didn’t harm herself, just had a 30 year old two year old tantrum, and gave it up. Her intended audience was gone.