They can fight altered too. Plenty of altered males (and females) are dog aggressive. Actually, neutered males tend to be the ones who start fights with unneutered males. Altering really doesn't do THAT much to change behavior. It's certainly not a magic fix for aggression.
More and more studies are linking early spay/neuter to various cancers, hip dysplasia, and CCL tears. Personally I won't alter any future dogs until at least 2 years of age when they are mostly done growing. That is not a good choice for everyone- an unaltered dog is much more responsibility and...
As a groomer, livestock guardian breeds are some of the ones I am most careful with until I know the dog. Even ones raised as pets generally do not take kindly to strangers messing with them! They're impressive at their job for sure.