These threads are always flashpoints and always the same people saying the same thing.
If the park concerned was an on-lead aread, then the owner was BU and I would have been angry myself if a loose dog had come bounding up to me and either my dcs or dogs, if it clearly should have been on the lead. I also object to the 'he only wants to play' thing, when that is clearly irrellevant, as the dog should have been under control regardless.
Fundamentally, just as with many things, there are good people and bad people - so good dog owners and bad dog owners. Good owners take the time and care to train their dogs properly, clean up after them and take all steps to make sure they don't adversely affect anyone else. Bad dog owners do not, simple as that, as usual it tends to only take a few bad dog owners to give all owners a bad name.
Not all dogs have reliable recalls, even when trained extensively, a responsible owner should/would be aware of this and make sure they have a) trained some alternative control behaviours, such as an instant down and b) are aware enough of where their dog is and what its doing when out walking to be able to stop them from running up to other people, by keeping them on the lead if necessary and only making the effort to take them to places where they can safely be let off lead without bothering others.
That said, I have noticed that more and more children seem to be afraid of dogs these days than ever before. Every single one of my dc's school friends that have come to play at our house has been terrified of dogs and my dogs have to be locked in the garden every time as a result. Similarly there are lots of children that squeal, flap and run away making a huge fuss when I am walking with my dogs and they are calmly walking to heel - on the lead. If I see a person, child or adult, who looks nervous or scared, I always step aside and put my dogs into a down until they have passed, but I still get dirty looks and sometimes comments, despite having well trained, calm, friendly dogs.
As for the comment, nobody NEEDS a dog. That is technically true, unless perhaps you have a seeing-eye, hearing or other assistance dog or you work with police, army, security dogs, or for that with matter epilepsy or cancer detection dogs - or Pets As Therapy dogs. Dogs give an awful lot to our society and ask for very little in return (eg a warm bed, regular meals, fresh water and some freedom to run off-lead). They bring a lot of happiness to a lot of people and yes, some people are afraid of them, but that doesn't automatically mean that they should be eliminated from our society.
To come back to my original point, the dogs of responsible dog owners are not a problem. Unfortunately getting hold of and keeping a dog is all too easy in this country. They are treated by many as disposable playthings and the amount of care, training and responsibilty they require is neither considered nor cared about by these people. Tarring every dog and every owner with the same brush and calling all owners and dogs bad is neither accurate or fair.