There is no harm at all in teaching your dog to accept wearing a muzzle. There are many times in his life where it may be necessary, and if he is comfortable with wearing it that will make things all the better for him (and you!). http://www.morrco.com/trdogtowemu.html
Dog aggression can occur in any breed of dog, though it can possibly be more common in this breed. http://www.badrap.org/dogdog-tolerancehttp://www.badrap.org/sites/default/files/dog_dog.pdf
There is also a lot you can do to safely manage your dog, figure out what his tolerance levels are, and train him to not act like an ass around other dogs. http://www.badrap.org/node/99http://www.badrap.org/node/98
Some dogs that are dog aggressive can have other dog friends, some can not. That is something a reputable, responsible trainer could help you figure out safely. This can be a good place to find a trainer, as well as possible recommendations from folks here on the forum. http://www.apdt.com/
Guage is beautiful - thank you for adopting him!