lvwhitebir, you are grossly confusing two entirely separate issues.
Subjectivity means that something is a matter of opinion, that there is no objective truth with respect to it. Surf or ski, burger or pizza. Italian rock opera or fusion jazz. Matters of taste or preference are subjective.
Things like the suitability of punching or grappling are matters of situational appropriateness or suitability for the individual but remain empirical, objective realities. They can be tested scientifically, even if there are individual differences that mediate decisions based on that science.
For instance, take the practice of clinical nutrition.
1) There are different OBJECTIVES: weight gain, weight control, longevity, strength and endurance, adaptation to a medical condition, adaptation to a spiritual observance such as veganism, etc.
2) There are INDIVIDUAL DIFFERENCES: People respond differently to different foods, for instance for me, phenylalanine is completely inoccuous. For persons with certain congenital conditions who cannot metabolize it, it's very dangerous. Some people can't take gluten, or lactose, or whatever else. Some people taste the bitterness of certain vegetables (such as Brussel sprouts) far more strongly than others, it's genetic. Not me, I love them, they're like eating candy.
3) There are UNKNOWNS: no one claims to know all there is to know about every substance a person can ingest, all the interactions and synergies, etc. We know a lot, and we don't know a lot. So some judgement calls have to be made.
But no one would for a moment suggest that those three qualifications mean that clinical nutrition is subjective, that it is a matter of opinion, that eating anything is just as good as anything else. Sure, you could take two kinds of foods and say that one isn't unequivocally better for you than another. But you can say that one does one thing and the other does another, and that they are both a hell of a lot better than a big mac and fries. That is an objective truth. Meanwhile, someone will point out that one big mac won't kill you. But that is also an objective truth, not a subjective one. It is an OBJECTIVE TRUTH that eating white rice is nutritionally identical to eating a bowl of candy, with the exception that it is far less cariogenic. Many cultural Chinese think that it's the staff of life--it's not. There's practically nothing in it but a single complex carb. Nutritional science TELLS us what's in it, and that it's not very nourishing. It doesn't matter that one billion people (and my grandmother) think otherwise. It's true. That's objective.
Indeed, what works in one case, for one person, may not in another set of circumstances. I'm not suggesting otherwise. But number one, this does not make it subjective. Number two, it should make us regard a more robust, resilient, and versatile approach as more effective than those that are not.