Horse racing (and other sports) insider information is an odd edge case in betting. You can't get rid of it, since the owner/trainer will always know more than the public. So it is grudgingly accepted. Using it as justification for other, preventable insider-information abuse is plain wrong.

The fact that it is a bet, and might not always pay out, is irrelevant. If you keep using insider information, on average you will profit from it.