Grandson with dog phobia

WWMk2, Trisher I completely agree with your perspectives.
It's not irrational and his fear should be met with understanding - he's only 9. A bit of discussion about why some dogs behave that way and letting him help devise the strategy for avoiding the dogs in a matter of fact way would seem to me to be all that's needed.

I was thinking when I was 9 I walked to and from school with a group of friends, there was a part of the grass verge we avoided because we knew there was a fairy ring there. We also knew there were aliens living in the sewers under the pavement. Now that was irrational! Goodness knows what would happen to me if I'd had those ideas today.

Like LuckyGirl and others I wouldn't call this a dog phobia.
It's a natural fear of big noisy aggressive dogs, which I share because of past experiences.
Although I also agree that they're only doing their job of protecting their home and family.
Different breeds for different jobs - not all the same.
Nandalot a puppy could be a good idea but make sure it's the right breed with the right parents.