Each year, thousands of racehorses are killed in abattoirs. As a nation, we cannot justify this cruelty. 

My law firm usually celebrates the Melbourne Cup the Sydney way: with fascinators, champers, a TAB punt, and three minutes of screaming at the TV.

Then we saw the revelations on ABC's 7.30 about what the horse racing industry quaintly calls "wastage", or what I'd call "the calculated annual slaughter of thousands of healthy horses".

Collectively, we decided that we were done.

We tweeted our decision to our 4000-or-so followers. Knowing what we now knew, we were simply choosing to no longer celebrate or support the racing industry.

Each year we also tweet that we won't be celebrating Australia Day on January 26. Nobody much cares. But let casually slip that you're skipping a horse race, and my goodness...

Our tweet has been retweeted and liked more than 5000 times, and we've been interviewed by Virginia Trioli and the chief racing writer at The Age.

We have also copped a mother lode of abuse. I won't go into it, hilarious as it is, but I am spellbound by the passion we have unleashed.

The whole thing is just so Australian. As a nation we famously don't give a shit about much, but there are a lot of people here who clearly feel a desperate and visceral insistence that everyone (I mean everyone) must honour The Cup.

But let's consider the actual issue; what we find is a mathematical equation followed by an ethical one.

The maths is brutally simple: as exposed by 7.30, the Australian racehorse breeding industry produces around 13,000 thoroughbred foals each year. These horses have an average racing life of two or three years, but should live until 25-30. Consequently, about 8500 horses are unceremoniously "retired" from racing each year.

I didn't know this until the 7.30 report aired. The racing industry, however, has known it all along.

This brings us to the ethical question: are we OK with an industry which fulfills its purpose -- running horse races for our entertainment -- on the production of thousands of horses that cannot realistically be offered the opportunity to live the full length of their natural lifespan?

This is qualitatively no different from the greyhound racing industry, which involves the deaths of some 18,000 dogs a year. There's no getting around it. And all the money that the industry is now promising to throw at "humane treatment" of retired racehorses can't reconcile the equation.

Sure, as base-level morality, the industry owes the horses a less horrible death than 7.30 showed they've been getting, but it's still death.

Is this OK? It's not OK by me.

After the tweet, I was accused of having selective ethics -- and that's spot on. All ethics are selective; they're not innate. We can all make a decision on this, as we can on any other issue.

Obviously the critical mass of people remain overwhelmingly on board with racing and betting on racing -- particularly on the iconic Melbourne Cup. Our tweet tapped into a deep well of national identity.

Can the maths change that? What about the death of War Ends, one of the hundreds of thoroughbreds tortured and killed at a Queensland abattoir in less than a month, secretly filmed for 7.30? War Ends won $400,000 in prize money for his owners, before his life was ended in conditions that should shame us all.

There's nothing evil about racing, per se. It could be done in a way that doesn't hurt horses beyond the inherent physical risk of the sport itself. That would mean fewer horses and slower races but, if the fun is really in watching and betting, it would lose no popularity.

How will we, as a nation, navigate our way to a new landing point on the sport of kings? The status quo is untenable and we know it. Are you celebrating the Melbourne Cup this year? If not, what could get you back on board?