"His culture" is just another compromise from the secular world to put a dent in your Christian walk. Words that trouble you, upset you, foul language, crass jokes, on and on, all of that is those arrows from Satan mentioned in the Full Armor of God. I have no idea what your boyfriend says, but if they trouble you enough to post on a forum, then I am guessing they aren't acceptable and we know when we are being exposed to sin in our gut. We know.
Just remember, you faith is Christ, Jesus Christ is always going to be your number one relationship.
Colossians 4:6
Let your speech always be with grace, as though seasoned with salt, so that you will know how you should respond to each person
Is your boyfriend Christian who is sincere in growing in faith, then the problem will solve itself. He should welcome the chance to leave behind sin. As he grows in Christ, he will turn from sin, "his culture" will become simply, Christian. However, if he is spiritually stagnant, that can cause trouble. If he isn't Christian, then that's a whole 'nother ball game.
From my own personal experience, when the Lord's name is used in vain around me; I always feel compelled to speak up, hey that offends me and that offends God. A lot of people don't use it around me anymore. LOL
Anyway, my two cents is you and him need to discuss it and why it makes you upset in the larger scope of being a Christian.
Mark 3:25
If a house is divided against itself, that house will not be able to stand.
Discords that fester can and will have a impact on relationships over time.