We were partially blocking an aisle at the grocery store when another shopper clipped my back with her cart. I turned around and said, "oh gosh sorry, I didn't realize I was in the way." A few minutes later, she and her daughter were blocking the aisle. Our daughter was driving the toy car cab in the front of the cart. She said sweetly, "excuse me, excuse me." The teenage daughter looked at me with her lips pressed tightly. I said, "she's learning to speak up for what she needs." The reply was, " Oh, I guess at her age, she can get away with that, I'd get yelled at."
I'd much rather have someone know their needs and make a request, then hit me with her cart. Once our daughter is speaking more than simple phrases, we'll teach her to say, "excuse me, would you mind moving so I can pass?"
It isn't rude to know what you need and ask nicely, especially if your intent is to honor everyone's needs equally, including safety.