Gambling is not a profession I think someone should get into and I dont think taking money from people in the gambling profession (and this includes owning casinos) is such a good idea. Unfortuantly these people who make money this way have alot to give and people are more than willing to take their money since they have alot.
IMO it was a chilul Hashem, not that they owned a race horse or that it was run on Shabbos, but there was an idea that a Race horse can get a bracha for a donation