I absolutely agree that hitting a dog ever is bad and repeatedly in particular is really, really awful.
We all know that what happened was very bad. Sometimes people do do things they really regret and never repeat them again though.
It's great the OP is getting training and help.
What we don't know, unless I missed it in which case sorry, is how old the dog is, how long the OP has had the dog or whether the dog has ever done anything like this before.
Those saying she should have not taken on a dog aggressive dog or should have trained it out of the dog are taking it for granted that this was a known issue.
I have a large dog who was passed to me by someone who I trusted, they told me the dog was perfectly fine with other dogs.
I was careful and didn't take chances on someone else's word but everything was fine for the first few months.
One day my dog suddenly barked and lunged at another dog it had, up till that point, been interacting very happily with - I was not paying close enough attention to prevent it from occurring but was luckily quick enough to grab my dog before it escalated.
Now flowergirl24, we have controlled on the lead walks when there are other dogs around, we have nice loose, long lead walks when we walk in areas/times that other dogs are expected but not within sight.
Recall is super important so we do a lot of maintenance on that because if I don't do it "just because" frequently and not just when it is needed, DDog would forget.
I changed my walk times a little (which I am fortunate enough to be able to do) and DDog gets off lead, crazy bounce about time when I am absolutely sure (ha!) no other dogs are going to pop up, and if they do I can recall and pop the lead on quickly before DDog gets a chance to go bounding over - which is disconcerting in itself purely because of his size and regardless of intent.
I'll not trust DDog with strange dogs off lead or just left to his own devices on the end of the lead now.
However I now know that DDog is fine after being carefully introduced to a particular dog over time which suggests to me that there is anxiety or fear tied up in meeting strange dogs - understandable, I feel the same about people DDog!
Maybe even if people are angry at the OP we could have a few more tips and discussion on how to prevent these situations rather than just "training needed", even if the OP is disingenuous it could be helpful to others - and me! Any other tips gratefully received here!
Incidentally I want Myoldbeans to be my friend now, after their very good post.