Popa:
1) read any vegetarian or animal-welfare arguments, Jewish or not, and you’ll see that the living conditions, and not the slaughter itself, is the overwhelming focus of their concerns.
2) upside down is not technically necessary — standing shechita is definitely practiced today. There are also different ways of upside-down shechita, some of which are more humane than others (shackle-and-hoist has been banned in the US since 1958 and the Rabbanut bans it and has even been trying to prevent its South American importers from using the practice.)