> I wouldn't call that a fundamental principle.
Okay, you have your definition and you can dream of some utopian world where everyone practices your own morality.
The thing is, all you've done is shift the topic to what 'injustice' means.
The US court case which established the right to strike, Commonwealth v. Hunt, specifically highlights how union action is not necessarily injustice but may have a "proper purpose". Quoting https://web.archive.org/web/20150123211142/http://www.lovkoa... :
"The manifest intent of the association is, to induce all those engaged in the same occupation to become members of it. Such a purpose is not unlawful. It would give them a power which might be exerted for useful and honorable purposes, or for dangerous and pernicious ones. If the latter were the real and actual object, and susceptible of proof, it should have been specially charged. Such an association might be used to afford each other assistance in times of poverty, sickness and distress; or to raise their intellectual, moral and social condition; or to make improvement in their art; or for other proper purposes. Or the association might be designed for purposes of oppression and injustice. But in order to charge all those, who become members of an association, with the guilt of a criminal conspiracy, it must be averred and proved that the actual, if not the avowed object of the association, was criminal."
The moral argument is that you have the right to do as you wish, limited to legal and moral restrictions. You need to demonstrate that the result causes injustice, not assume it exists.
> I personally am not an opportunistic person in that sense.
I personally find it very boring to have a discussion with people who make up their own non-standard definitions to justify their position.
> striking is not a moral right either
Then why should anyone care? Many legal things in the US are not based on moral rights. Where is the moral right to fire an employee? What is the moral right to restrict the presidency to persons 35 or older?