Looking at this angle I don't think the tackle was too high.
The initial challenge for the ball might not look high but the contact with the opposition players shin clearly is high.
Why has he ended up planting on the middle of the shin? Because he rolled over the top of the ball. Why has he rolled over the top of the ball? He's tackled too high up on the ball. If you tackle middle of the ball or lower then you cannot possibly plant your studs in the middle of the oppositions shin.
The issue with this argument is so many people on here seem to genuinely believe Casemiro only has 2 options.
1. Don't make the tackle at all
2. Make the tackle and unavoidably plant his studs in the middle of the oppositions shin.
We all know this isn't true. There's a 3rd option. You make the tackle without rolling over the top of the ball, winning it cleanly and we win the ball back and don't even concede a free kick. He was favourite to win the ball, he should have tackled more responsibly and won the ball without even conceding the foul, and we wouldn't be having this discussion.
I'm sure there's been similar or worse challenges gone unpunished. I sincerely hope our players are going out on the pitch thinking "I'll just plant my studs in the middle of the oppositions shin because I saw someone else get away with it the other day in a different game". Have some fecking game intelligence and stop giving the referees a decision to make.