The problem is that you changed the argument.

And never acknowledged mine. I acknowledged that you believe that the inherently dangerous tackle makes it red (or possibly red) just like Kompany's. You said Kompany's studs may have been a little higher. Then you also called it late. Then you said he never intended to go for the ball.

1. It's not a late challenge. That's indisputable.
2. His studs are not up. At all.
3. There's a picture of him looking directly at the ball while lunging directly at it. Not sure how you can claim he's not going for it.
4. Sliding through legs. There's nothing in the rules against it. Proper tackles go through the legs all the time and never get called. Hell, James Milner completely upended Neymar in the Champions league this year. I think he may have done the same to Sterling a year or so ago. Proper challenge, through the legs. No foul was even called. However, if you miss the ball, you are going to see yellow.
5. That leaves intent. You believe that he has intent to be going for Aguero and take out his legs. I believe that the intent is obvious. He's making a tactical foul going for the ball.

Where we disagree is with Kompany. You are trying to draw a connection between a discretionary/judgment call above with his definitive situation. Kompany's tackle was improper by the book. There's no judgment call to make there regarding intent or anything. It doesn't matter if he's going for the ball or not. He's studs up to the leg. That's a red card by the book. And it's my OPINION that there should be some discretion where the contact was avoided and a red could spoil a wonderful match. That's an unwritten rule, and one that I believe was probably the underlying reason why red wasn't given.