This is true, but also apart from siblings, it's probably rare that a 14 year old would be hanging out or playing with a 7 year old. Unless at a childminders which is where something happened to my DD.
Slightly different scenario with ages but recently we had an autistic boy at DDs childminder. DD is 3 and the boy who pushed her is 8. He really hurt her and we had to take her to hospital due to the bump on her head making her sick.
Sadly, due to the safety of the other children, the boys contract was terminated immediately.
Although i desperately feel for the parents who are trying to work, we all want our children in a safe environment.
As PP said, as parents we keep our children away from danger regardless of the circumstances and sadly that means some children will be excluded. A 14 year old boy can be a big strapping strong lad, or on the smaller side, but regardless, will be a hell of a lot bigger and stronger than a 7 year old.
To push a 7 year old over to the point they had sand in their mouth must've been quite a violent shove, and I would not want DD around that again just like I didn't want DD around the lad that shoved her. Shoves and pushes happen, but shoves and pushes at lead to injuries are not in the normal realms of children's rough play. But your DH sounds totally incompetent, and you can't even enjoy any alone time with your friend due to this. His laziness is at your expense and it's not fair at all.