I think some people seem to be of the rather skewed and misinformed opinion that the purpose of a day's racing is to kill as many horses as possible.
The purpose of a day's racing is to celebrate the fastest horses and the best jockeyship. The ideal outcome for everyone who goes racing is to watch exciting sport and see all the participants come back safe and sound.
There is a risk, and the stakeholders within racing are actively working to minimise that risk, but it will never be completely eliminated. Horses die from freak accidents in the field, from heart attacks anywhere, so there will be some inevitable deaths. But no one celebrates those deaths, or enjoys them, or gets any kind of "fun" out of them.
It amuses and frustrates me in equal measure that every time there is a dog lover v dog hater thread, as soon as a dog lover says or implies that their dog is more important to them than another human (e.g. someone else's child) they are, not unreasonably, treated as though they have confessed to sacrificing babies at a Black Mass. But once a year, without fail, you get the "horses are just as important as people" mob briefly raising their heads above the parapet.
And as for "no-one who truly cared for animal welfare would have anything to do with it" - that is utter bullshit. It's precisely because so many racing fans and participants are concerned with animal welfare that racing is so carefully regulated and scrutinised, that a percentage of every pound bet in a betting shop goes towards animal health research and rare breed preservation, that the modifications already discussed at length have been made.
Yes, racing is a multi-million-pound industry - it brings in over £270 million in tax every year. But that is not automatically mutually exclusive with striving for continuous improvements in equine welfare.
It's notable that those who have posted in support of racing have posted facts while many (not all) of those opposed to it have had to resort to the usual hysterical, hyperbolic emotional and inaccurate rhetoric.