Speaking right is important because it shows your beliefs and your stand on matters arising. Furthermore, the odds of you saying the wrong things are also lowered.
So what happens when you have to mix with people who have different values or beliefs from you? Well, there is such a thing as non-conforming, and keeping to a standard.
So if my friends swear, I would usually not participate. Why not you might say? Why yes is what I would say. Simple reason is I have very little compulsion to swear.
The fact is, I use my mouth to praise Jesus. And I use it to speak good things. So to use it to swear, is not very smart in my opinion. Anyway, your choice.