[motives]

I don't usually like engaging in political discourse online, as its very rarely fruitful, but I'd just like to encourage you to study some philosophy before making statements like these whereby you treat your own opinion as absolute fact (or at least your phrasing comes off that way to me). The nature of inaction on these issues is not necessarily inherently immoral, and I would personally argue its supererogation rather than moral duty, so whilst it may be commendable to stand up in these sorts of situations, in my opinion you are by no means morally obliged. This whole area has been a subject of debate for a very long time and the answer is never as simple as a generalisation that can fit in a sentence or two.

[madeofpalk]

There was never any assertion that not participating is immoral, but that it is itself choice.

[bollu]

Could you name some pointers that I should look up to learn more about both sides of this debate?

[motives]

Sure, with respect to the language used in the original post, modal logic can be used as a formal basis for how we derive meaning from phrases like 'must' and 'never'. This has a lot of overlap with the field of deontology, which is a subset of moral philosophy which looks more closely at moral dutys and obligations. There are quite a few different theorys worth exploring in moral philosophy beyond just the deontological one, so I'd recommend starting with classical perspectives like that of Kant and making your own way from there.