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?