What about 5. Linkage to another belief that causes us to associate so-called masochistic behavior with something good?
Some people like BDSM because they like the feeling of someone being else in control. Some people like being hit because they associate it with the love of their parents. Some people wallow in bad feelings because that's how they learned to get attention.
I think question 2 is an important one. These behaviors can be logically grouped together as "masochistic', but the kinds of "bad" that they move towards are completely different. You're talking physical pain, confusion, fear, exhaustion, self-judgment, identifying with "suffering," etc. I don't think there's anything to be gained by combining them into one category. If we want to talk real masochism, I think the cleanest solution would be to stick with the enjoyment of physical pain.
Anyone gonna weigh in on the old pleasure and pain two-sided coin?
You might be right; in which case there's no underlying motivational mechanism, and no reason not to split off any one behavior (whether SM or being Bruce) and eliminate it if we choose to, without fear of harming our enjoyment of the others.
That would be disappointing, because if there is an underlying mechanism, it would have interesting psychological and ethical consequences. (I'm biased towards conclusions that have more consequences. Is that an irrational but useful bias?)
Followup to Stuck in the middle with Bruce:
Bruce is a description of masochistic personality disorder. Bruce's dysfunctional behavior may or may not be related to sexual masochism [safe for work], which is demonized by most people in America. Yet there are ordinary, socially-accepted behaviors that seem partly masochistic to me:
Question 1: Can you list more?
Question 2: Doubtless some of the behaviors I listed have completely different explanations, some of which might not involve masochism at all. Which do you think involve enjoying pain? Can you cluster them by causal mechanism?
Question 3: When we find ourselves acting masochistically, should we try to "correct" it? Or is it part of a healthy human's nature? If so, what's the evolutionary-psych explanation? (I was surprised not to find any evo-psych explanations for masochism on the web; or even any general theory of masochism that tried to unite two different behaviors. All I found were the ideas that sexual masochism is caused by bad childhood models of love, and that masochistic personality is caused by other, unspecified bad experiences. No suggestion that masochism is part of our normal pleasure mechanism.)
Some hypotheses:
My guess is that, if it's a side-effect (e.g., 3) or a non-causal association (4), it's okay to eliminate masochism. Otherwise, that could be risky.
These all lead up to Question 4, which is a fun-theory question: Would purging ourselves of masochism make life less fun?
ADDED: Question 5: Can we train ourselves not to be Bruce without damaging our enjoyment of these other things?