Take a sport like boxing. Kicks, elbows, and knees are against the rules in that sport, as in you will be disqualified from the match and otherwise face sanctions if you utilize those techniques. You can therefore expect these attacks will not to be used in a boxing match, thus a boxer has no need to learn how to use or defend against them. And, a boxer may justly exclaim "You suck!!! You have no honor!!!" to an opponent who kicks him in the nuts and is immediately disqualified.
If these rules and their accompanying sanctions did not exist, it would not be boxing, it would something else, like Muy Thai. In this case it is tactically advantageous and downright necessary for a Muy Thai fighter to use kicks, elbows, and knees as appropriate. And no one cries foul on being kicked, elbowed, or kneed in a Muy Thai match, because those techniques are clearly allowed and inevitably ubiquitous. If they did so, they would be morons, right?
Now let us apply similar thinking to the "sport" of the AH MA...