I don't think that was rude. In most situations, I'm all for allowing dogs to meet each other. I let Jackson go up and greet other dogs, big and small, but I first scope out the situation. First off, retractable leashes kind of suck in these situations... I only use a retractable if we're in a big field or a beach or something. I just don't think you have the control (specifically for a large dog) you could with a regular 6 foot leash.
Yesterday, in Petco, there was a very excitable pit bull puppy (5 1/2 months old) and I let Jackson go up and greet him because the owners had him under control on a regular leash, as I did w/ Jackson. There's only been 1 situation where I actually had to pick Jackson up and help him because a dog was just WAY too hyper and rough. Usually they work it out themselves, Jackson helped the Pit pup yesterday by being calm and totally ignoring his excitable behavior, therefore the pit calmed down. They fed off each others energy and the owner was glad I allowed them to meet because they want to get their dog socialized too obviously. Same thing, once there was a 1year old Rottie in the store and I allowed Jackson to go up and meet him, and the owner was sooo thankful because she wants him to be social but if nobody were to allow him to meet other dogs, how would that happen?
But anyways, I don't think you were being rude! Your dogs, your choice! You're just being a good mom.