Ask my dad and he'll tell you how nasty racing greyhounds can be with other dogs.

He's had one of his own dogs rushed to the vets a few years ago when his brother attacked him and made a real mess of him and the sister decided to join in too and some of them go completely potty whenever they see another dog when out being walked.
Not far from where I live, there was an incident where a dog walker had his dog attacked and killed by two greyhounds and the owner of them just walked past and did nothing.

I've also seen other greyhound owners walking their dogs on lead on the fields where I walk mine and they would go totally potty whenever another dog came into view.
Even on the dog track, fights between the dogs aren't uncommon, especially when the race is finished thats why they wear the cage muzzles and many of them wear box muzzles when not racing to stop them going for each other. My dads dogs often wear them.
He used to have dogs at a proffessional greyhound kennels and I painted one of the kennel owners retired greyhounds and, when I was looking round the place, many of those dogs were wearing box muzzles when they were in their kennels.

Yes, when hyped up on high protien diets, racing greyhounds are often neurotic but they calm right down once retired.

My dad says his dogs see other small dogs they don't know as prey rather than other dogs. He says they'd kill little dogs if they got hold of them.

I suppose it is partly how they are reared and always in kennels and walked only on lead and not socialized with other dogs outside etc...

Even at the track, they are often kept muzzled...they don't let the greyhounds play together and get to know each other, put it that way.

I have personally seen lots of racing greyhound show aggression so I know they can be that way. I'm sure the ones I saw being walked on our local fields would have run straight over and gone for my dogs had they not been on the lead. He'd walk about 5 at once, you could tell they were racers.