I guess it's better than cutting their tongues out Rabits? There's also a citrus spray collar which seems to do the job.
I wouldn't like to be the one who gets caught putting an electric collar on a greyhound, there's the difference? There's a whole lot more to it than just the cruelty factor.
When I was a kid walking to and from school every day I used to have to walk past a property that had horses and lots of dogs, including a german shepherd that had it's tongue removed. I was always terrified of this animal and held my breath in fear as I walked past hoping it wasn't anywhere around. Occasionally I'd hear something behind me and feel the hot breath of it's silent barking, terrifying for a kid of primary school age. Couldn't wait to get my first bike and run the gauntlet to school.