Slaughter houses in Canada is a large part of the reason our horse industry is doing so well, there are fewer cases of abuse, neglect and unwanted horses than in the states because there is somewhere for the unwanted horses to go. Look through American Craigslist and you'll find hundreds of sorry looking skinny horses for free or cheap, they're a rarity in Canada BECAUSE when someone can't care for their horse they have somewhere to send it. I would MUCH rather a horse experience a quick death and then be put to good use than see it standing starving in a field, abused or not a neglected life is a sad life.
I am 100% for slaughter, and while it does make my heart ache more so than the slaughter of other 'food animals' because I have a personal connection to horses, my 'rational side' knows that what it boils down to is the fact that horses are livestock.
OP, I haven't seen any tempers come out yet. Just people stating their opinions, that isn't a bad thing and I commend you for admitting your naivety. It's something a lot of us have done over the years, as I don't imagine very many people spent their early years believing horse slaughter is a "good" thing. Maybe some of the opinions here will open your mind a little?