That’s where the official’s judgement comes in and it can be decided by review. Tackling high can be more natural, and can be done legally. The point is to get the ball carrier to the ground, not obliterate him. That end has proliferated with each advance in equipment, it seems.
If a ball carrier lowers his head to a tackler, then call offensive targeting. They desire to punish an opponent goes both ways.
What got me in the games yesterday was the number of penalties for facemark violations, both defensive and, especially, offensive.
Every now and then your hand will find a face mask and use it when you are tackling and you should pay for it, big time. What I caught more was D players using a face mask hold - "Just for a second! I let go!" - on WRs going down field well before the ball was thrown. Now that has to be a trained technique. It interrupts the route but isn't - "I swear!!" - an intentional foul. Horse pucky. It's a foul or should be.
Then there were the OLs doing the same trick to stop DLs on the rush or during the shoving matches we euphemistically call "blocking" these days (except at the academies, of course). This is "illegal use of the hands", a new and even more euphemistic way to call out a face mask penalty. And these definitely are trained behaviors; it's becoming more and more common to see it. And it should be sanctioned more than it is until it goes away.
I'd make face masking 15 yards and a loss of down. It's dangerous and it needs to be emphasized to the coaches that everybody sees it.