How do you keep quiet when teenagers have no respect for your family?

My family went on a walk last night and there were a group of teenager behind us that were cursing like sailors! My 5 year old asked why these girls were cursing and what the words meant and I told her we'd talk about it later (and we did). But I have a 5 year old, 2 year old and a 9 month old. I don't want them exposed to that kind of speech at such a young age, especially when we don't use those words in our house. My husband kept on wanting to turn around and tell them to take their dirty filthy mouthes away from our children's ears. I don't blame him, but I was afraid of some whacky parent running up and yelling at us for reprimanding their foul mouthed teens. We kept walking and sped up our pace to get away from them. I know it's not unusual to hear that kind of thing from teenagers now (sad though), but they stayed literally right behind us for a good 20 minutes and cursed the entire time. How can anyone keep quiet around such rude children?