Yes, except condemning someone on assumptions is less reasonable than assuming innocence. That's sort of how justice systems work, you know. Presumed innocent until proven guilty. Ring any bells? We only have the officer's word as to what happened. There were no other witnesses. Condemning him is the less rational of the two.
As it stands, I'm trying not to assume either way. I'm taking that stance that there's no way of knowing, because frankly there isn't. We have no way to determine if he was telling the truth at all. And if we can't prove guilt or innocence either way, all the assumptions in the world don't mean shit.
Dog had a limp? So what? As has been stated numerous times, dogs with arthritis that normally limp are capable of running if they damn well please. And quite fast at that.
Dog was old? Fun fact.
Senility can cause increased aggression and irritability in dogs. Not that I am asserting that this dog is senile, I'm merely pointing out that age does not necessarily mean it will be less aggressive than a younger dog.
No history of violence? Well of course not. Most dogs with that are violent towards humans are usually put down if they cause any serious injury. That doesn't stop dog attacks from happening. Non-violent dogs can snap without warning. Especially with strangers, especially if there's no one around that the dog knows or considers part of its "pack". As has already been stated.
So it's possible the officer was lying, and it is possible he was telling the truth. Now, if you want to condemn someone based on assumptions, that's your business, but it's pretty fucking stupid in my opinion. I for one believe that the dog probably wasn't acting aggressively and the officer misjudged, but I am not so full of myself - nor so unhinged from reality - as to believe my assumptions should carry any sort of weight, or that because I believe something to be more likely then it must be true.
For the record, either way I believe an apology is in order. Pets are considered family members, and not apologising over something like that is pretty fucking cold.
And this post was a lot longer than I intended it to be...