As I read this story, I note that the persons opposed to the slaughterhouses claim to be concerned about protecting "wild" horses.
Then I read this passage:  "She said that consumption of horse meat is dangerous for humans because of the drugs and medications horses consume during their lives."
Maybe I'm wrong, but it seems to me that truly "wild" horses just wouldn't be wandering around our western states taking drugs, whether in the form of medication or otherwise.  And I have a hard time believing, particularly in these days of limited budgets, folks are venturing out onto the prairie to inject or otherwise fill "wild" horses with drugs of any sort.
That leads me to one of two conclusions:  Either 1) We're dealing with "wild" (or, more properly, truly feral) horses that are generally drug-free, and so a good and safe source of protein (eveer said "I'm so hungry that I can eat a horse?"  I know that I have, and if this alternative is true, perhaps we'll have that opportunity soon), or 2) The horses, by-and-large, are not truly "wild" at all, but rather consist largely of unmarketable nags that were dumped onto public lands by former owners who kept their meds up to date in the relatively recent past, but now either could not or chose not to maintain such animals any longer (in which case they constitute an invasive feral population that should be treated in a manner equivalent to feral hogs, silver carp and Burmese pythons in the Everglades).
Either way, insisting on keeping hordes of these stray critters alive doesn't seem to be particularly logical or rational, or in the interest of the ecosystems that they have invaded.
 

Well said, Charlie.