Dog park dilemma/ recommendation on actions

Wondering if I am overreacting. I was at the dog park and everything was fine except there was a dog that got a little to rough with the other dogs. Well he went after my dog and he was mainly just growling and grabbing his neck. Well I got in between the two and decided to leave (the other owner was not interfering like usual). He kept going after Luno (whose is 60lbs and 6mo). Well I just calmly said be nice to the other dog multiple times as I got between them holding my dog by his collar. Then the dog was able to get past me and he bit Luno in the side hard enough for him to yelp which at that point I yelled at the dog and kept yelling till he backed up!!! I was so angry I wanted to hit the dog!!!!

The owner didnt make any kind of notion to stop and only after I yelled at her dog did she grab him!!!! And then let him go and he ran right back to us at the door!!! UGH I hate irresponsible owners.

Well anyway my BF says I should let him go because he need to learn to defend himself.... just in case I'm not their one time. But it should never have to come to that. Should I not grab my dog by the collar because he may think he doing something wrong? I don't wan tLuno to turn into a scared dog... He 98% around good dogs at the park and he always does great! Its just every once in awhile there are horrible owners there and I leave as soon as it gets to be a problem!!!

What do you guys do in this situation and what recommendations do you have?