Ok .. I'm feeling slightly badly about my outburst yesterday regarding off-lead dogs. Especially as the other pet owner was so completely understanding and friendly. I've decided to do the following to address Kassa's "other dog" issues.
Firstly I'm switching back to the "gentle leader". The greyhound rescue folks originally had him on this type of leader instead of the Martindale collar. I was a bit surprised at this because they also said he walks with you pretty well and doesn't tug on the leash. I think they had him on this because with the gentle leader you can quickly and easily pull his head to the side. There were a few dog encounters we had earlier where I did this and the result was far less stressful.
I also picked up a can of "Spray Shield" which is supposed to be a pain free way to deter aggressive dogs. I should be able to use this on a loose dog or Kassa as the case may warrant.
Lastly I have initiated contact through Dogs & Kat. The rescue group had a pamphlet of hers with the reading material. I hope she can recommend some program to help socialize Kassa better. Jennifer over at neversaynever greyhounds earlier recommended that I have Kassa be a fly on the wall in a dog training program. This would help him become more comfortable with other breeds.