I disagree with the thought that one has a moral obligation to do something about something you find immoral. What argument would you put forth to defend such a statement?
Why does the commenter believe there is ever a point at which a person becomes morally responsible for the acts of others?
As for arguments about why you would ever act, it really depends on the person. Most people are far more pragmatic about what it constitutes for their family to be safe and happy whereas others believe (along with their families) that "It is better to die free than to live in shackles."
I've noticed the latter especially among immigrants from regions with a history of totalitarian regimes. For example, the majority of Russians who immigrated here after the USSR collapsed remember all too well what it's like to live in an oppressive state. For them, they see history repeating itself and know first hand how arguments like "who cares if you've got nothing to hide" end in people disappearing in the night and neighbors ratting each other out for petty reasons. It is very alarmist but when you're born without the cultural trust for government in America, you see things very differently.
As for harmful to a minority, you're thinking of winner-take-all electoral processes. Democracy is usually meant to describe the overarching idea of self-rule with checks and balances. I can't think of a single democracy in the developed world that doesn't have a minority-friendly self correcting feature (whether or not the checks and balances are working properly is a different matter).
To me it comes down to, do you "believe" in democracy or do you actually BELIEVE in democracy? The former means that you don't actually give a shit about the type of government you are ruled by until it infringes on you and yours. The latter means that to you, living in a democracy and being free (from oppression, surveillance, an over-zealous majority, etc.; whatever freedom is for you) is as important an aspect of your identity as your job or your family.
[1] http://www.amazon.com/Sociopath-Next-Door-Martha-Stout/dp/07...
* E.g. dominant frameworks are: morals are that which is necessary as a matter of integrity and self-respect, morals are that which you would prefer all people strictly adhere to, morals are that which provide the greatest good to the greatest number, morals are that which promote the state (or increase compassion, or knowledge).
By that definition everyone is acting immorally at all times when they're not attempting to remedy the most immoral thing they are aware of occurring at any given time. Such a definition fails the "usefulness" test.
People are not acting immorally at all times when they're not attempting to remedy the most immoral thing, as long as their moral framework indicates not acting (or continuing an ongoing action) is more moral. Should I donate all my money to charity? No, so long as, for example, I am concerting my efforts to use that money toward a greater moral goal.
Notice that I have insisted on the balance (there may be times when you do not have to do something or simply you cannot do anything reasonable: f.ex. 'give all the money I earn to fight poverty' or 'give all my time to the needy', these may be or may not be done, it depends).
In the end, the people who make these kind of decisions are mostly called heroes.
I cannot explain it better: morality is all about this: what must/must not and what can/cannot be done. Otherwise, there is no 'morality', just 'feelings'.
I'd have to see the causal link between some abstract thing happening to me and another (similar but different) abstract thing happening to you, but until someone shows this causal link, it's a fallacy.
Are you going to call the police or pretend nothing happened so you can reduce the risk you would lose your job?
What are your morals?
This is the point where I assert the existence of morality as an axiom. I have no more argument than "it fits better with my understanding of the world. Actually, its opposite does not fit at all."
However, I guess this is shared by many many others.
And because of both, like with Peano's, I am willing to accept it and (because of the nature of what I am accepting), hold it even to my death (or so I hope).