Yeah, I used to believe that one should abide by such rigid doctrines and rules to govern their choices in any situation.
Really, it all depends on the situation. For instance, regarding the one where your opponent is cheating to win, in some situations I would rather lose than compromise my integrity. Like playing monopoly with kids or something. Or there may be a situation where even though someone is playing dirty, I can still beat them. But when my opponent is maybe a corrupt manager at work, trying to fuck with my livlihood, I would be willing to fight dirty.
The point is, deciding ahead of time that this or that way is how you want to handle all the different situations and choices you will have to make in life is stupid. It’s lazy. You’re basically trying to make it so you don’t have to think critically ever again because you’ve already decided ahead of time that in any situation “the gloves will come off,” or that you “won’t fight dirty.” Each different situation should dictate your course of action. Otherwise, you aren’t applying what you learned. You’re life’s equivalent of a guy standing in an assembly line, screwing legs into chairs forever.