As a dog owner and a runner I see both sides of this one.
My dog is very well behaved now but that's because I've put a lot of work and time into him. It's not ok for dogs to be out of control, even friendly ones.
And a lot of people can't read doggy body language so don't know when they're over excited v aggressive. Yet the owners don't understand this because they know their dog.
If you feel that strongly about it, 'no worries' shouldn't be your response.
I run with my dog past a VERY neurotically aggressive collie. When he is on the lead and sees my dog, the hackles go up, the teeth are bared and he tries to frenetically bite through his lead.
Once he was loose in the road and I thought that he was going to attack, I'm used to all sorts of dogs but this one needs some serious work done with him.
Next time we come in contact I've decided that I will confront the owners and talk to them about it.