Often those reasons are that TBTB want to misbehave.
e.g., my sympathies are entirely with the "Stansted 15", and I would consider that they had acted reasonably, and with moral justification, if they had gone even further and damaged the plane to prevent it leaving.
Lets take a look at that in detail shall we ?
First assumption is that TPTB were misbehaving. I believe they were acting within the law as laid down - I think the law, and the way it's being applied, in that area stinks. But in legal terms, TPTB in that case were carrying out their assigned duties and enforcing the law as it's laid down. I'm thinking it's getting time to go and see my MP in person, and ask why my letters on the subject have not been answered. But that is a completely different discussion.
Now, as to the 15. Yes, I agree that their actions had moral justification. Was it reasonable, well that's an area wide open to debate - but as far as they went, maybe.
Then your last bit. You are stating that you consider it acceptable to cause criminal damage to the property of someone (or some business) acting fully within the law and in support of lawful actions by officials tasks with enforcing the law. Lets be clear, you wrote
"I would consider that they had acted reasonably, and with moral justification, if they had gone even further and damaged the plane". There is no room for misunderstanding there, you are stating that you would consider them justified in causing criminal damage.
Further, your justification for that is that the law and the actions of those enforcing it are morally unacceptable.
Who decides which "moral rules" apply ? If it's morally acceptable to cause criminal damage because you disagree with the law, where does that stop ? Surely, by your logic it would be quite acceptable for ... lets rummage around for an example ... people of some religious beliefs to damage property (eg throw paint on the house, vandalise the car) of of a gay or lesbian couple ? Similarly, by your own argument, it would be acceptable for members of certain groups to damage the salons of anyone who cuts or shaves beards. I could go on - there are many activities that are morally unacceptable to some group or other, and some of those groups have gone down the "militant" route with nasty consequences.
With your post, you have demonstrated why we must have strict limits on what people can do in taking the law into their own hands. Without those restrictions, it's a free for all to cause damage (or worse) if something offends your specific set of morals. That is the road back to crowd justice and lynch mobs