Puppy has broken three collars trying to get at the dogs that walk by with owners?

Castration won't automatically solve any existing problem. It can cause or exacerbate fear-related problems in less confident dogs.

 
I so doubt this. Certainly castration won't fix a problem caused by fear, but how can it exacerbate fear-related problems? Dogs tend to go through "fear periods" during the adolescent phase of life, which is of course by coincidence shortly after the time when most dogs are neutered. The neutering isn't causing the fearful behavior. Inappropriate owner response to fear during these fearful periods can cause them to become permanent patterns of behavior.
 
The vast majority of dog bites to humans and to other dogs are delivered by unneutered males. A simple operation makes your dog immediately much safer to the general public. It's not just about preventing unwanted puppies.

Bingo, mudpuppy.
Most dogs that end up in shelters due to behavior problems are unneutered males age 9 mos. and up.  They are also the most likely to bite.
I also disagree that a dog needs to be trained before spending time with other dogs - what they need is to spend time with other *puppies* right from the get go while they are being trained, which is why I keep telling Damarcus that his dog needs puppy class *yesterday*!!!!  If I owned this dog, I would have had the pup in class by age 10 weeks. 

Amen!!!!

Well, I have seen uneutered males as well as intact males.  In my experience neutering is not the solver of aggression and biting. It may calm them down but if they are already agressive that is ingrained.  Neutering  is a good thing to do.  This pup needs training and should be fixed for health reasons and so on and so forth. 

Having a dog go through a "fear period" is different to having a dog with a fearful disposition IMO. 
 
It must be very different here because it doesn't seem to be true that most dogs are neutered at puberty.  Most people I know (myself included) allow the dog to mature fully before going ahead.  The dog I was referring to was 5yo when he was done. 
 
Sure the dog probably needs puppy classes.  What I meant was he's coming into close proximity of something which makes him reactive and hasn't had the training to deal with it or give his owner control.  I think that's the most concerning issue.  The fact stands that a rott isn't like any other dog.  They are large, powerful and willful with a natural tendency to guard and protect.  Neutering will not change that.  It may calm him down - but even if it does thats a very small piece of the jigsaw.  Plus if he's already 7months old he will already have testosterone storming round his body and it could be months before this goes away.
 
Firestorm was right, a rott has to be whiter than white - an ambassador for his breed.  Chopping his nuts off won't make the dog more suited to the owner, or the owner more able to deal with this breed.  Training, a good class, maybe one to one with someone who has breed experience.... those are the things that will make the real difference and they need to be done now before someone gets hurt and/or the breed gets blackened further.

I would have to agree with those saying to get a stronger collar.  My experience is with pit bulls who are also extrememly strong dogs.  I was watching my friends pit a few years ago and he had a nylon collar with a snap closure.  He was tied up outside (we were all outside too) and he saw a cat and took off.  I'm  telling you, the collar didn't even resist, it just snapped right off his neck.  After that, I'll never put a collar with a plastic snap on my guys.  I always use buckle collars and none have ever broke like that.

Well everyting depends on the way you are walking the dog, if you let him for one second to pay attention to the other dog then you will loose the fight, the key is to re direct his attention even before he forgets about the rest of the world to get to the other dog, the leash has nothing to do with this situation, you need to have a better control on your dog and that can not be achieve even if you have him in a chain

Have you tried a prong, or a martingale collar?