I would have to see a replay but I think there were 2 other players pretty close to it.
You can end someone's career by not even fouling them. The injury has nothing to do with whether it's a foul, or a yellow or red - so that's the first thing.
I don't think it was out of control. I don't think it was high. I don't think it was a lunge with both feet off the ground.
People get hurt in football. The idea you shouldn't be able to tackle unless you're 100% sure you won't hurt them is complete nonsense.
It should have been a foul and a yellow card. That's it.
Anything above where the ankle is is a high tackle. If you watch the tackle again you'll see that at the point of impact both his legs are off the ground, he is elevated. The moment you become elevated, you are out of control, you can't slow yourself down as the only thing that determines where you go is the trajectory at which you launch yourself into the tackle. The only way he can do that is by going into the tackle by jumping, hence it's a lunge. It's an unsafe tackle, end of. Hence he was stretched off, probably with something broken.
In the academy's up and down the country kids are being taught how to tackle safely. You are meant to slide into the challenge with one leg going along the ground and with your studs either facing downwards or away from the player (if it's a hook slide tackle). Wes Browns method of tackling will definitely not be shown to them as the way to do it.
I agree with you where you say people get hurt in football, it's a contact sport, but incidences like this can be minimised if there is a 0 tolerance stance on poor challenges.