Why do you think that the idea of "morally dubious Callum" is so prevalent in the fandom?
I think there are a couple of reasons why, some good some bad. All of this is just speculation, but imo, some of the more positive/neutral reasons are:
It's angstier (and thus, less predictable story-wise) if Callum isn't just a straightforward good guy.
It creates a much more morally ambiguous story if both sides are willing to do dubious things, which can be more intriguing and engaging than others.
It makes Callum more complex if his morality is a bit questionable.
However, there's more than a handful of pretty terrible rationales that I've spotted over time.
The spooky factor to dark magic has warped people's sense of right and wrong, and categorize simply casting dark magic in of itself as always evil regardless of the circumstances (I say "casting" because apparently Harrow, Sarai, and Amaya are not ever judged by the fandom for either using dark magic or helping gather the materials for it).
Since a few of the "morally dubious" traits people cite often sound a lot more like Rayla, there may be some projection going on, as people try to deflect her traits onto Callum. For instance, temper, ruthless, devotion.
Speaking of projection, I think some fans see Rayla as a wish fulfilment character, and thus see Callum's main purpose as essentially "serving" Rayla, either by protecting her, helping her, or most importantly, destroying himself and his moral code for her (because then all that is left is total and unquestioning loyalty to her).
I also think there might be a subsconscious desire to prove that Rayla is somehow "better" than Callum. This was especially true pre-timeskip, when fans were adamant at saying that Rayla is stronger than Callum, is faster than Callum, is more noble than Callum, will live longer than Callum, is taller than Callum, etc. Now that Callum has either caught up or eclipsed Rayla on most of these, I think there's added pressure to argue that Rayla is still nobler than him, and the way to do that is to argue that he would do things she would never consider doing.
Anyway, that's my take. Feel free to agree or disagree.













