No it’s not. Like others have mentioned. There are many instances where you could be diving with shoulder and have offensively player change direction and you make contact with you helmet. Regardless of your “Stone Age” teachings players typically don’t tackle with their damn face mask straight up. That may not be political correct but it’s the truth.
Keep your head up and look at what you are hitting it won't matter what the offensive player does. Good grief man I was seriously taught to tackle head up in the early 1980s. Tackling with your head down is how you get paralyzed and killed. This ain't some new discovery, spearing has been illegal forever, to protect the tackler. Head down tackling has never been legal.