Parenting....The way it is today?

I am the 1st one to say that I am not the perfect parent and really none of us out there in this world are. I enjoy taking my daughter to our local city parks and wading pools. Sometimes it is so frustrating because you are raising your child one way and then they go into the world and learn exactly what you are trying to not teach them. The other day we were at the wading pool and at least when I was growing up my mother taught me to not splash the parents that were there. To share our things and be courteous of others and their property. I didn't get to go to the wading pool on my own ever so it is a shock to me me that there are so many older children there from the ages of 8 all the way to about 12yrs of age with no supervision. It's frustrating because you not only have to parent your own child but you almost have to parent these other kids. Most of them are great and are very well behaved but every now and again you run into a bad apple, like I did yesterday. The first thing he did was swore and it wasn't shit or damn....he used the f-word while talking to one of his little buddies and we were right there and heard it plain as day. So, I told him to watch his mouth or next time I was going to walk him back to his house and give his parent or parents a little piece of my mind. He then proceeded to try to tease this wonderful special needs girl from our neighborhood who was there with her little sis and I am assuming their nanny who was deep into a book and did not hear or see a thing. My daughter has played with these two girls a few times when we have been at the park, so I felt I should say something and did give this boy who could not be older then 10 a piece of my mind and asked him to leave her alone and to go play with his friends. I just feel like we need to show our kids with our actions how to behave and if another parent does not, then I feel we have to step in and show these children the right way to act. They might not like you at that moment but I feel that maybe this will be something this young boy will learn from in the future or at least I hope so. Was I out of line or are there others like me out there that speak their mind to these young ones? I just feel I have to say something because this is not how I was raised and the world has changed so much from when I was a child, which was not that long ago. I know that young man was very happy to see me leave the pool but I do feel very good that I spoke my mind.