954 I agree with you 100% on this. I am not a big fan of dog parks for that very reason. I much prefer play dates with dogs that you know your dog gets along with. Adult dogs by nature really do not have any desire to be social butterflies anyway.
The best way within reason is to deal with the unexpected rude dog with obedience (calling your dog away with a “come” or “leave it”) If it is impossible because of the other dog’s continued engagement I have no problem intervening with a spray shield blast if the other dog’s owner doesnt call him/her off. If it is done to protect your dog or the other dog from being bit (even in defense) it is called for and it is harmless.
Best bet is to manage the situation by avoiding it in my opinion.