I believe most slaughtered horses are domestic, not mustangs.
You are correct.
Mustangs ARE included in the slaughter.
Still--doesn't this bother you? You want your tax dollars paying for this? What if it were dogs?
You are correct. The little secret in all of this is that the price of a horse as meat provides a base level to it's value. The price of a pleasure horse on the market would drop if selling excess animals for meat were outlawed.