Despite popular belief banning horse slaughter will not reduce neglect and improve animal welfare.
Some people do not have the means to humanely euthanize their horse(s). Some people don't even have the means to feed their horse(s) and can't find a buyer.
Slaughter in the past was inhumane due to inappropriate equipment and lack of regulations.
Banning it will not stop it--it will just continue out of country. If slaughter exists wouldn't you prefer to keep it under your supervision.
Having one in the States will prevent long hauls causing injury, fatigue, malnutrition, and even death.
Sadly, horses aren't a companion to everyone.
Would you rather a horse starve to death(or go to unregulated slaughter house) or be slaughtered under strict regulations making it humane as possible?