Its not irrelevant at all and its this sort of thinking that is wrong with all dog owners. They think because it wont kill someone or the damage is lesser, their shitty behavior is acceptable. Its not.
You expect a certain behavior from a Pit Bull. You should expect the same behavior from any dog. Just because the outcome may be different doesn't excuse any dog, big or small, from being aggressive.
If my dog is on lead and is controlled at a park, and there is a small aggressive yapper and I tell the owner several times to control their dog and they dont. That is not cute. Thats aggressive and I wouldnt blame my dog for reacting. However, the obedience trainer in me would not allow my dog to react.
Ok lets use another example. Im 6'5", I weight 110kg. Is it fine if a 5'5" person is aggressive to me? If they were pushing me and swearing at me (similar to nipping and growling is for a dog) would you expect me to cop that and walk away? No, id do it right back. Its not my problem that Im bigger therefore the affect is greater.